Information recording medium and reproducing apparatus thereof

ABSTRACT

An information recording medium is at least composed of a substrate having a microscopic pattern constituted by a continuous substrate of grooves formed with a groove portion and a land portion alternately, a recording layer formed on the microscopic pattern for recording information, and a light transmitting layer formed on the recording layer. The microscopic pattern is formed with satisfying a relation of P≦λ/NA, wherein P is a pitch of the land portion or the groove portion, λ is a wavelength of reproducing light for reproducing the recording layer, and NA is a numerical aperture of an objective lens. The land portion is formed with wobbling so as to be parallel with each other for both sidewalls of the land portion. An auxiliary information based on data used supplementally when recording the information and a reference clock based on a clock used for controlling a recording speed when recording the information is recorded alternately. Information is recorded in the recording layer corresponding to only a land portion by at least either one change of reflectivity difference and refractive index difference in the recording layer so as to be more than 5% for reflectivity and so as to be more than 0.4 for modulation amplitude of signal recording.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an information recording mediumthat is particularly used for recording information and a reproducingapparatus for reading out information recorded in the informationrecording medium with making the information recording medium moverelatively, particularly, relates to an information recording medium forrecording and/or reproducing information optically and a reproducingapparatus thereof.

[0003] 2. Description of the Related Art

[0004] Until now, there existed a system used for reading outinformation from an information recording medium while the informationrecording medium is made relatively move. In order to reproduce thesystem, such a method as optical, magnetic or capacitance is utilized. Asystem for recording and/or reproducing information by the opticalmethod has been most popular in daily life. In the case of a read-onlytype information recording medium in disciform, which is reproduced by alight beam having a wavelength of 650 nm, for example, such a medium indisciform as a DVD video disc pre-recorded with picture imageinformation, a DVD-ROM disc that is pre-recorded with a program or like,a DVD audio disc, or an SACD (Super Audio CD) disc that is pre-recordedwith musical information is popularly known.

[0005] In the case of a recording and reproducing type informationrecording medium, there existed a DVD RAM disc utilizing a phase changeeffect, an ASMO (Advanced Storage Magneto-Optical) disc and an iD(intelligent image disc) utilizing a magneto-optical effect.

[0006] On the other hand, in order to increase recording density, such astudy as shortening a wavelength of laser beam so as to realize emissionof violaceous light has been continued. A second harmonic oscillatingelement or a semiconductor light emitting element of gallium nitridesystem compound, which was invented recently, emits light having awavelength λ in the neighborhood of 350 nm to 450 nm. Consequently, theyare possible to be an important light emitting element, which increasesrecording density drastically.

[0007] Further, a design of objective lens complying with such awavelength has been advanced. Particularly, an objective lens having anNA (numerical aperture) utilized for a DVD disc, that is, an NA ofexceeding 0.6 and more than 0.7 is being developed.

[0008] As mentioned above, a reproducing apparatus for informationrecording medium that is equipped with a light emitting element of whichwavelength λ is reduced down to 350 nm to 450 nm and equipped with anobjective lens of which an NA is more than 0.7 is being developed. Byusing these technologies, it can be expected that an optical discsystem, which surpasses recording capacity of current DVD disc furthermore, will be developed.

[0009] Further, it is also desired that an information recording mediumhaving higher recording density, which is designed on the basis of aviolaceous laser beam and a higher NA, is developed.

[0010] On the other hand, a recent recording and reproducing type discadopts a microscopic configuration, namely the land-groove system. Withreferring to FIGS. 41 and 42, an information recording medium designedfor a higher NA recording and reproducing system is explained.

[0011]FIG. 41 is a cross sectional view of a conventional informationrecording medium adopting the microscopic configuration that is calledthe land-groove system according to the prior art.

[0012]FIG. 42 is an enlarged plan view of the information recordingmedium shown in FIG. 41 showing the horizontal configuration of theinformation recording medium according to the prior art.

[0013] As shown in FIG. 41, an information recording medium 100 iscomposed of a recording layer 120 and a light transmitting layer 110that are sequentially laminated on a substrate 130. A microscopicpattern 131 is formed on the substrate 130. The recording layer 120 isformed directly on the surface of the microscopic pattern 131. Themicroscopic pattern 131 is composed of a plural of land portions “La”and “Lb” (hereinafter generically referred to as land portion “L”) and aplural of groove portions “Ga” to “Gc” (hereinafter generically referredto as groove portion “G”). Macroscopically, the configurationcorresponds to that the microscopic pattern 131 is constituted by acontinuous groove composed of the land portion “L” and anothercontinuous groove composed of the groove portion “G”.

[0014] Further, as shown in FIG. 42, a record mark “M” is formed in boththe grooves composed of the land portion “L” and the groove portion “G”respectively when recording.

[0015] With paying attention to the dimensions of the microscopicpattern 131, while a shortest distance between the groove portions “Ga”and “Gb” is assumed to be a pitch “P0” (another shortest distancebetween the land portions “La” and “Lb” is also the pitch “P0”), themicroscopic pattern 131 is formed so as to satisfy a relation of P0>S0,wherein “S0” is a spot diameter of reproducing light beam.

[0016] Hereupon, the spot diameter “S0” is calculated by a wavelength λof laser beam for reproducing and an NA of objective lens such asS0=λ/NA. In other words, the pitch “P0” is designed so as to satisfy arelation of P0>λ/NA.

[0017] In the case of the information recording medium 100, a light beamfor recording (recording light) is irradiated on the light transmittinglayer 110 and a record mark “M” is formed on both the land portion “L”and the groove portion “G” of the recording layer 120.

[0018] Further, a light beam for reproducing (reproducing light) isirradiated on the substrate 130 or the light transmitting layer 110 andreflected by the recording layer 120, and then the reflected reproducinglight is picked up for reproducing.

[0019] Inventors of the present invention have actually manufactured aninformation recording medium 100 as an experiment, and experimentallyrecorded and reproduced the information recording medium 100. Theinventors founded a problem such that a cross erase phenomenon wasextremely noticeable. The cross erase phenomenon is a phenomenon suchthat information is recorded with being superimposed on a signalpreviously recorded in a groove portion “G”, for example, when recordingthe information in a land portion “L”. In other words, it is such aphenomenon that information previously recorded in a groove portion “G”is erased by recording another information in a land portion “L”.

[0020] Further, this phenomenon can also be noticeable in a reversecase, that is, the cross erase phenomenon is also recognized ifpreviously recorded information in a land portion “L” is observed whenrecording information in a groove portion “G”. If such a cross erasephenomenon occurs, as mentioned above, information recorded in anadjacent groove is damaged. In case of an information system havinglarger capacity, an amount of lost information becomes excessivelylarge. Consequently, affection to a user is enormous.

[0021] Consequently, it is considered for such an information recordingmedium 100 that information shall be recorded only in either landportion “L” or groove portion “G”. However, there is existed a problemsuch that recording capacity of an information recording medium willdecrease and a merit of the information recording medium having apotential of recording in higher density will decline if such aninformation recording method is conducted.

SUMMARY OF THE INVENTION

[0022] Accordingly, in consideration of the above-mentioned problems ofthe prior art, an object of the present invention is to provide aninformation recording medium that is reduced in cross erase and can berecorded in higher density, and an reproducing apparatus for reproducinginformation recorded in the information recording medium with making theinformation recording medium move relatively.

[0023] In order to achieve the above object, the present inventionprovides, according to an aspect thereof, an information recordingmedium at least comprising a substrate having a microscopic patternconstituted by a continuous substrate of grooves formed with a grooveportion and a land portion alternately; a recording layer formed on themicroscopic pattern for recording information; and a light transmittinglayer formed on the recording layer, the information recording medium isfurther characterized in that the microscopic pattern is formed withsatisfying a relation of P≦λ/NA, wherein P is a pitch of the landportion or the groove portion, λ is a wavelength of reproducing lightfor reproducing the recording layer, and NA is a numerical aperture ofan objective lens, and that the land portion is formed with wobbling soas to be parallel with each other for both sidewalls of the landportion, and that an auxiliary information based on data usedsupplementally when recording the information and a reference clockbased on a clock used for controlling a recording speed when recordingthe information is recorded alternately and continuously.

[0024] According to another aspect of the present invention, thereprovide a reproducing apparatus for reproducing a recording layer of aninformation recording medium comprising: a substrate having amicroscopic pattern constituted by a continuous substrate of groovesformed with a groove portion and a land portion alternately; therecording layer formed on the microscopic pattern for recordinginformation; and a light transmitting layer formed on the recordinglayer, the information recording medium is further characterized in thatthe microscopic pattern is formed with satisfying a relation of P≦λ/NA,wherein P is a pitch of the land portion or the groove portion, λ is awavelength of reproducing light for reproducing the recording layer, andNA is a numerical aperture of an objective lens, and that the landportion is formed with wobbling so as to be parallel with each other forboth sidewalls of the land portion, and that an auxiliary informationbased on data used supplementally when recording the information and areference clock based on a clock used for controlling a recording speedwhen recording the information is recorded alternately and continuously,the reproducing apparatus comprising: a light emitting element foremitting reproducing light having a wavelength λ of 350 nm to 450 nm anda noise of less than RIN (Relative Intensity Noise) −125 dB/Hz; areproducing means equipped with an objective lens having a numericalaperture NA of 0.75 to 0.9; and a control means for controlling thereproducing means to irradiate the reproducing light only on the landportion for reproducing.

[0025] Other object and further features of the present invention willbe apparent from the following detailed description when read inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0026]FIG. 1 is a cross sectional view of an information recordingmedium according to a first embodiment of the present invention.

[0027]FIG. 2 is an enlarged plan view of a microscopic pattern of theinformation recording medium shown in FIG. 1.

[0028]FIG. 3 is another enlarged plan view of a microscopic pattern ofthe information recording medium shown in FIG. 1 exhibiting a state ofbeing recorded.

[0029]FIG. 4 is a cross sectional view of the information recordingmedium shown in FIG. 1 exhibiting a state of reproducing or recording arecording layer of the information recording medium.

[0030]FIG. 5 is an enlarged plan view showing an auxiliary informationarea and a reference clock area in the information recording mediumaccording to the first embodiment of the present invention.

[0031]FIG. 6 is an enlarged plan view of the information recordingmedium according to the first embodiment of the present invention wheninformation is recorded in the information recording medium through theCLV (Constant Linear Velocity) recording method.

[0032]FIG. 7 is an enlarged plan view of the information recordingmedium according to the first embodiment of the present invention wheninformation is recorded on the information recording medium through theCAV (Constant Angular Velocity) recording method.

[0033]FIG. 8 is an enlarged plan view of the information recordingmedium in disciform according to the first embodiment of the presentinvention when information is recorded in the information recordingmedium through the CLV recording method.

[0034]FIG. 9 is an enlarged plan view of the information recordingmedium in disciform according to the first embodiment of the presentinvention when information is recorded on the information recordingmedium through the CLV recording method and further the information isrecorded on a land portion.

[0035]FIG. 10 is an enlarged plan view of a photo-detector mounted on anapparatus for reproducing an information recording medium according tothe present invention showing a state of dividing the photo-detectorinto four.

[0036]FIG. 11 is a first example showing a distributed recording ofauxiliary information.

[0037]FIG. 12 is a second example showing a distributed recording ofauxiliary information.

[0038]FIG. 13 is a third example showing a distributed recording ofauxiliary information.

[0039]FIG. 14 is a fourth example showing a distributed recording ofauxiliary information.

[0040]FIG. 15 is a table exhibiting data change before and aftermodulating a base-band.

[0041]FIG. 16 is a table exhibiting an example of actual data changebefore and after modulating a base-band.

[0042]FIG. 17 shows a first example of an amplitude-shift keyingmodulation waveform according to the present invention.

[0043]FIG. 18 shows a second example of an amplitude-shift keyingmodulation waveform according to the present invention.

[0044]FIG. 19 shows a third example of an amplitude-shift keyingmodulation waveform according to the present invention.

[0045]FIG. 20 shows a first example of a frequency-shift keyingmodulation waveform according to the present invention.

[0046]FIG. 21 shows a second example of a frequency-shift keyingmodulation waveform according to the present invention.

[0047]FIG. 22 shows a third example of a frequency-shift keyingmodulation waveform according to the present invention.

[0048]FIG. 23 shows a first example of a phase-shift keying modulationwaveform according to the present invention.

[0049]FIG. 24 shows a second example of a phase-shift keying modulationwaveform according to the present invention.

[0050]FIG. 25 shows a third example of a phase-shift keying modulationwaveform according to the present invention.

[0051]FIG. 26 shows a first example of a shape of the informationrecording medium according to the present invention.

[0052]FIG. 27 shows a second example of a shape of the informationrecording medium according to the present invention.

[0053]FIG. 28 shows a third example of a shape of the informationrecording medium according to the present invention.

[0054]FIG. 29 is a cross sectional view of an information recordingmedium according to a second embodiment of the present invention.

[0055]FIG. 30 is a cross sectional view of an information recordingmedium according to a third embodiment of the present invention.

[0056]FIG. 31 is a cross sectional view of an information recordingmedium according to a fourth embodiment four of the present invention.

[0057]FIG. 32 is a cross sectional view of an information recordingmedium according to a fifth embodiment of the present invention.

[0058]FIG. 33 is a block diagram of a first reproducing apparatus of aninformation recording medium according to an embodiment of the presentinvention.

[0059]FIG. 34 is a block diagram of a second reproducing apparatus of aninformation recording medium according to an embodiment of the presentinvention.

[0060]FIG. 35 is a flow chart showing a reproducing method of aninformation recording medium according to an embodiment of the presentinvention.

[0061]FIG. 36 is a block diagram of a recording apparatus of aninformation recording medium according to an embodiment of the presentinvention.

[0062]FIG. 37 is a flow chart showing a recording method of aninformation recording medium according to an embodiment of the presentinvention

[0063]FIG. 38 is a graph exhibiting a relation between reflectivity anderror rate.

[0064]FIG. 39 is a chart exhibiting reflectivity and reproductioncharacteristics of embodiments 1 through 7 and comparative examples 1and 2.

[0065]FIG. 40 is a graph exhibiting a relation between modulationamplitude and error rate.

[0066]FIG. 41 is a cross sectional view of a conventional informationrecording medium according to the prior art.

[0067]FIG. 42 is an enlarged plan view of the information recordingmedium shown in FIG. 41.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0068] [First Embodiment]

[0069] With referring to FIG. 1, a basic configuration of an informationrecording medium according to the present invention will be explained.An information recording medium according to a first embodiment of thepresent invention is such an information recording medium that at leastone of recording and reproducing is conducted through an optical method.Actually, it is such an information recording medium as a phase changerecording type information recording medium, a dye type informationrecording medium, a magneto-optical type information recording medium ora light assist magnetic type information recording medium.

[0070]FIG. 1 is a cross sectional view of an information recordingmedium according to a first embodiment of the present invention. In FIG.1, an information recording medium 1 according to the present inventionis at least composed of a light transmitting layer 11, a recording layer12, and a substrate 13 formed with a microscopic pattern 20. They areformed sequentially on the substrate 13. Unevenness of the microscopicpattern 20 forms a shape of continuous substance of approximatelyparallel grooves, wherein a symbol sign 21 is a microscopic pattern thatis recorded with a record mark “M” as shown in FIG. 3.

[0071] Further, a shape of the information recording medium 1 can beapplicable in any shape such as disciform, card and tape even incircular, rectangular or oval shape. The information recording medium 1can also be acceptable although it is perforated.

[0072] Furthermore, a light beam for reproducing (reproducing light) orrecording (recording light) is irradiated on the light transmittinglayer 11.

[0073] The substrate 13, the recording layer 12, and the lighttransmitting layer 11 are detailed first. The substrate 13 is a basesubstance having a function of sustaining mechanically the recordinglayer 12 and the light transmitting layer 11 sequentially laminatedthereon. With respect to a material for the substrate 13, any ofsynthetic resin, ceramic and metal is used. A typical example ofsynthetic resin is various kinds of thermoplastic resins andthermosetting resins such as polycarbonate, polymethyle methacrylate,polystyrene, copolymer of polycarbonate and polystyrene, polyvinylchloride, alicyclic polyolefin and polymethyle pentene, and variouskinds of energy ray curable resins such as UV ray curable resins,visible radiation curable resins and electron beam curable resins. Theycan be preferably used.

[0074] Further, it is also acceptable that these synthetic resins aremixed with metal powder or ceramic powder.

[0075] With respect to a typical example of the ceramic, soda limeglass, soda aluminosilicate glass, borosilicate glass or silica glasscan be used. With respect to a typical example of the metal, a metalplate such as aluminum having no transparency can be used. A thicknessof the substrate 13 is suitable to be within a range of 0.3 mm to 3 mm,desirably 0.5 mm to 2 mm due to necessity of supporting mechanically theinformation recording medium 1 totally. In case that the informationrecording medium 1 is in disciform, the thickness of the substrate 13 isdesirable to be designed such that the total thickness of theinformation recording medium 1 including the substrate 13, the recordinglayer 12, and the light transmitting layer 11 becomes 1.2 mm, for thepurpose of interchangeability with a conventional optical disc.

[0076] The recording layer 12 is a thin film layer that has a functionof reading out information, recording or rewriting information. Therecording layer 12 is formed with the microscopic pattern 20 that isconstituted by a plurality of land portions “L1” through “L4”(hereinafter generically referred to as land portion “L”) and aplurality of groove portions “G1” through “G5” (hereinafter genericallyreferred to as groove portion “G”) respectively. Information is recordedon either one of a land portion “L” and a groove portion “G” as a recordmark “M”. With respect to a material for the recording layer 12, amaterial that is represented by a phase-change material of whichreflectivity or refractive index changes in a process of before andafter recording or both of reflectivity and refractive index change in aprocess of before and after recording, a dye material of whichrefractive index or a depth changes in a process of before and afterrecording or both of refractive index and depth change in a process ofbefore and after recording, or a material represented by amagneto-optical material, which produces a change of Kerr rotation anglein a process of before and after recording, can be used.

[0077] With respect to an actual example of phase change material,alloys composed of an element such as indium (In), antimony (Sb),tellurium (Te), selenium (Se), germanium (Ge), bismuth (Bi), vanadium(V), gallium (Ga), platinum (Pt), gold (Au), silver (Ag), copper (Cu),aluminum (Al), silicon (Si), palladium (Pd), tin (Sn) and arsenic (As)are used, wherein an alloy includes a compound such as oxide, nitride,carbide, sulfide and fluoride. Particularly, alloys composed of a systemsuch as Ge—Sb—Te system, Ag—In—Te—Sb system, Cu—Al—Sb—Te system andAg—Al—Sb—Te system are suitable for the recording layers 12. Thesealloys can contain one or more elements as a micro additive elementwithin a range of more than 0.01 atomic % to less than 10 atomic % intotal. Such a micro additive element is selected out of Cu, Ba, Co, Cr,Ni, Pt, Si, Sr, Au, Cd, Li, Mo, Mn, Zn, Fe, Pb, Na, Cs, Ga, Pd, Bi, Sn,Ti, V, Ge, Se, S, As, Ti and In.

[0078] With respect to compositions of each element, for example, thereis existed Ge₂Sb₂Te₅, Ge₁Sb₂Te₄, Ge₈Sb₆₉Te₂₃, Ge₈Sb₇₄Te₁₈, Ge₅Sb₇₁Te₂₄,Ge₅Sb₇₆Te₁₉, Ge₁₀Sb₆₈Te₂₂ and Ge₁₀Sb₇₂Te₁₈ as for the Ge—Sb—Te systemand a system adding a metal such as Sn and In to the Ge—Sb—Te system asfor the Ge—Sb—Te system.

[0079] Further, as for the Ag—In—Sb—Te system, there is existedAg₄In₄Sb₆₆Te₂₆, Ag₄In₄Sb₆₄Te₂₈, Ag₂In₆Sb₆₄Te₂₈, Ag₃In₅Sb₆₄Te₂₈,Ag₂In₆Sb₆₆Te₂₆, and a system adding a metal or semiconductor such as Cu,Fe and Ge to the Ag—In—Sb—Te system.

[0080] With respect to an actual example of magneto-optical material,alloys composed of an element such as terbium, cobalt, iron, gadolinium,chromium, neodymium, dysprosium, bismuth, palladium, samarium, holmium,praseodymium, manganese, titanium, erbium, ytterbium, lutetium and tincan be used, wherein an alloy includes a compound such as oxide,nitride, carbide, sulfide and fluoride. Particularly, constituting analloy of a transition metal, which is represented by TbFeCo, GdFeCo andDyFeCo, with rare earth element is preferable. Further, the recordinglayer 12 can be constituted by using an alternate lamination layer ofcobalt and platinum.

[0081] With respect to an actual example of dye material, cyanine dye,phthalocyanine dye, naphthalocyanine dye, azo dye, naphthoquinone dye,fulgide dye, polymethine dye, acridine dye, and porphyrin dye can beused.

[0082] With respect to a method of forming the recording layers 12, afilm forming method such as a vapor phase film forming method and aliquid phase film forming method can be used. As a typical example ofthe vapor phase film forming method, such methods as vacuum depositionof resister heating type or electron beam type, direct currentsputtering, high frequency sputtering, reactive sputtering, ion beamsputtering, ion plating and chemical vapor deposition (CVD) can be used.

[0083] Further, with respect to a typical example of the liquid phasefilm forming method, there is existed a spin coating method and adipping and drawing up method.

[0084] The light transmitting layer 10 is composed of a material havingfunction of conducting converged reproducing light to the recordinglayer 12 while keeping the converged reproducing light in less opticaldistortion. A material having transmittance of more than 70%, forexample, at a reproduction wavelength λ, desirably more than 80% can besuitably used for the light transmitting layer 11.

[0085] It is essential for the light transmitting layer 11 to be lessoptical anisotropy. In order to suppress reduction of reproducing light,actually, a material having birefringence of less than ±100 nm,preferably ±50 nm by 90-degree (vertical) incident double paths is usedfor the light transmitting layer 11.

[0086] With respect to a material having such a birefringencecharacteristic, a synthetic resin such as polycarbonate, polymethylemethacrylate, cellulose triacetate, cellulose diacetate, polystyrene,copolymer of polycarbonate and polystyrene, polyvinyl chloride,alicyclic polyolefin and polymethyle pentene can be used for the lighttransmitting layer 11.

[0087] The light transmitting layer 11 can be provided with a functionof protecting the recording layer 12 mechanically and chemically. Withrespect to a material having such a function, a material having higherstiffness can be used for the light transmitting layer 11. For example,transparent ceramics (such as soda lime glass, soda aluminosilicateglass, borosilicate glass, and silica glass), thermosetting resin,energy ray curable resin (such as ultraviolet rays curable resin,visible radiation curable resin and electron beam curable resin),moisture curable resin and two-part liquid mixture curable resin arepreferably used for the light transmitting layer 11 having higherstiffness.

[0088] Further, a thickness of the light transmitting layer 11 isdesirable to be less than 0.4 mm in view of suppressing aberration whenthe information recording medium 1 is inclined.

[0089] Furthermore, in view of preventing the recording layer 12 frombeing scratched, the thickness of the light transmitting layer 11 isdesirable to be more than 0.05 mm. In other words, the desirablethickness of the light transmitting layer 11 is within a range of 0.05mm to 0.4 mm. More desirably, the thickness is within a range of 0.06 mmto 0.12 mm.

[0090] More, scattering of thickness in a single plain is desirable tobe ±0.003 mm maximum in view of spherical aberration, because an NA ofobjective lens is relatively large. Particularly, in case that an NA ofthe objective lens is more than 0.85, the scattering of thickness in asingle plain is desirable to be less than ±0.002 mm.

[0091] Moreover, in case that an NA of the objective lens is 0.9, thescattering of thickness in a single plain is desirable to be less than±0.001 mm.

[0092] With referring to FIG. 2, the microscopic pattern 20 that is oneof major features of the present invention is explained next. Asmentioned above, microscopically, the microscopic pattern 20 is composedof a continuous substance of approximately parallel grooves. However,macroscopically, the continuous substance can be in a shape of not onlylinear but also coaxial or spiral.

[0093]FIG. 2 is an enlarged plan view of a microscopic pattern of theinformation recording medium shown in FIG. 1. In FIG. 2, symbol signs“P” and “S” are a pitch between adjoining two groove portions “G2” and“G3” and a spot diameter of reproducing light beam respectively. Asshown in FIG. 2, a land portion “L” of the microscopic pattern 20corresponds to the land (raised) portion “L” shown in FIG. 1 and agroove portion “G” of the microscopic pattern 20 corresponds to thegroove (recessed) portion “G” shown in FIG. 1.

[0094] Further, the land portion “L” and the groove portion “G” can bewobbled, will be mentioned later. However, centerlines of the landportion “L” and the groove portion “G” are formed in parallel to eachother.

[0095] In case that a user records data in the information recordingmedium 1, the data are recorded only on either one of the land portion“L” and the groove portion “G”. Accurately, the data are recorded on aportion corresponding to either one of the land portion “G” and thegroove portion “G” in the recording layer 12. Selecting either the landportion “L” or the groove portion “G” is arbitrary. However, it isdesirable for selecting the land portion “L” or the groove portion “G”to maintain at least a same selection result of either the land portion“L” or the groove portion “G” even in any place in the recording layer12. In case of recording on different portions by a place, it is hard toreproduce continuously and resulted in degrading a recording capacitysubstantially.

[0096] In FIG. 2 and succeeding drawings FIGS. 3 to 9, a width of theland portion “L” and a width of the groove portion “G” is illustrated indifferent width in each drawing. However, it is understood that thewidth is not limited to one specific width.

[0097]FIG. 3 is a plan view of a microscopic pattern of the informationrecording medium 1 shown in FIG. 1 exhibiting an example of recordingthat is conducted only on land portions “L” of the recording layer 12.As shown in FIG. 3, a record mark “M” is recorded only on the landportions “L1” through “L4” not on the groove portions “G1” through “G5”,which constitute the microscopic pattern 21. The record mark “M” isrecorded by a mark position recording method or a mark edge recordingmethod.

[0098] A signal, which is used for recording, is a modulation signalthat is a so-called (d, k) code, which is defined as that a minimum marklength is “d+1” and a maximum mark length is “k+1”, wherein either afixed length code or a variable length code can be applied for a (d, k)modulation signal. Actually, with defining that a minimum mark length is2T, a (d, k) modulation such as (1, 7) modulation, 17PP modulation, DRLmodulation, (1, 8) modulation and (1, 9) modulation can be used.

[0099] A typical example representing the (1, 7) modulation of the fixedlength code is the “D1, 7” modulation (that is disclosed in the JapanesePatent Application No. 2001-80205 in the name of Victor company ofJapan, Limited). The “D1, 7” modulation can be replaced by the (1, 7)modulation or the (1, 9) modulation, which is based on the “D4, 6”modulation of the fixed length code (that is disclosed in the JapanesePatent Application Laid-open Publication No. 2000-332613). The 17PPmodulation is one of the (1, 7) modulation of the variable length codeand disclosed in the Japanese Patent Application Laid-open PublicationNo. 11-346154/1999.

[0100] Further, the (2, 7) modulation and the (2, 8) modulation, whichare the variable length code with defining the minimum mark length as3T, the EFM modulation, the EFM plus modulation, and the “D8-15”modulation (that is disclosed in the Japanese Patent ApplicationLaid-open Publication No. 2000-286709) as the (2, 10) modulation of thefixed length code can be used.

[0101] Furthermore, a modulation system, which defines the minimum marklength as 4T such as the (3, 17) modulation, and another modulationsystem, which defines the minimum mark length as 5T such as the (4, 21)modulation, can be used.

[0102] A groove portion “G” hereupon follows the definition shown in theTable 4.4-1 described in the publication “Understanding Optical DiscProperly” (edited by the Japan Patent Office and published by the JapanInstitute of Invention and Innovation in 2000). In other words, a grooveportion “G” is defined as a recessed groove previously provided spirallyor coaxially on a surface of base substance in order to form a recordingtrack.

[0103] Further, a land portion “L” also follows the definition describedin the publication. In other words, a land portion “L” is defined as aland portion previously provided spirally or coaxially on a surface ofbase substance in order to form a recording track.

[0104] Furthermore, the base substance hereupon is a name equivalent tothe substrate 11 of the present invention.

[0105] In FIGS. 2 and 3, with defining that a distance between adjoiningtwo groove portions “G2” and “G3” is a pitch “P” (in the same way, adistance between adjoining two land portions “L1” and “L2” is alsodefined as the pitch “P”), the pitch “P” is designated so as to satisfya relation of P≦S, wherein “S” is a spot diameter of reproducing light.The spot diameter “S” is calculated by a wavelength λ of laser beam forreproducing and an NA of objective lens such as S=λ/NA. In other words,the pitch “P” satisfies a relation of P≦λ/NA.

[0106] In case of using a violaceous laser beam, its wavelength λ iswithin a range of 350 nm to 450 nm, and in case of using a high NA lens,its NA is 0.75 to 0.9. Consequently, a pitch “P” is set to be within arange of 250 nm to 600 nm.

[0107] Further, in case of considering that a digital picture image ofHDTV (High Definition Television) program is recorded for approximatelytwo hours, more than 20 GB is necessary for a recording capacity.Consequently, the pitch “P” is desirable to be within a range of 250 nmto 450 nm. Particularly, in case that an NA is 0.85 to 0.9, the pitch“P” is more desirable to be 250 nm to 400 nm.

[0108] Furthermore, in case that a wavelength λ is 350 nm to 410 nm andalso an NA is 0.85 to 0.9, the pitch “P” is most desirable to be 250 nmto 360 nm.

[0109] A depth of groove portion “G” is preferable to be within a rangeof λ/8n to λ/20n, wherein “n” is a refractive index at a wavelength λ ofthe light transmitting layer 11. Since a reflectivity of the recordinglayer 12 is reduced a little due to existence of the microscopic pattern20, a depth of groove portion “G” is desirable to be shallower. Lessthan λ/10n is suitable for the depth of groove portion “G” as a limitfor jitter of a reproduced signal not to be deteriorated.

[0110] Further, an output of push-pull signal increases in accordancewith a depth of groove portion “G” when tracking down a land portion “L”or a groove portion “G”. Consequently, more than λ/18n is suitable for alimiting value for enabling to track. In other words, a range of λ/10nto λ/18n is suitable for a depth of groove portion “G”, and a mostsuitable range for the depth of groove portion “G” is λ/10n to λ/18n.

[0111] As mentioned above, the information recording medium 1 accordingto the first embodiment of the present invention is such an informationrecording medium that is recorded on either a groove portion “G” or aland portion “L” of the recording layer 12. Therefore, recording isconducted with keeping a distance of pitch “P” and resulted indecreasing the cross erase phenomenon.

[0112] Further, it is designed for the relation between the pitch “P”and the spot diameter “S” to be P≦S, so that recording density isprevented from decreasing.

[0113] A result of evaluation with respect to the cross erase phenomenonin comparison with a conventional information recording medium 100 isdepicted hereinafter. With respect to an information recording medium ofwhich recording layer 12 is formed by a phase change material, a secondtrack is recorded and reproduced, and the reproduced output is measured.Then, a first track and a third track is recorded ten times each with asignal having a frequency different from that recorded on the secondtrack, and an output from the second track is measured once again. Withdefining that an output difference between the outputs originallymeasured and secondary measured is a cross erase amount, a cross eraseamount cause by the conventional information recording medium 100 is −5dB. On the contrary, by the information recording medium 1 according tothe first embodiment of the present invention, a cross erase amount isreduced to the order of −2 dB. In other words, by using the informationrecording medium 1 according to the first embodiment of the presentinvention, a cross erase phenomenon can be improved by 3 dB incomparison with the conventional information recording medium 100.

[0114] Further, a similar evaluation is conducted to an informationrecording medium of which recording layer 12 is formed by amagneto-optical material. By the conventional information recordingmedium 100, an output decreases by 4 dB. On the contrary, by theinformation recording medium 1 according to the first embodiment of thepresent invention, an output decreases by just 1 dB. In other words, byusing the information recording medium 1, a cross erase phenomenon isimproved by up to 3 dB in comparison with the conventional informationrecording medium 100 although a magneto-optical material is used for theinformation recording medium 1.

[0115] Furthermore, a similar evaluation is conducted to an informationrecording medium of which recording layer 12 is formed by a dyematerial. By the conventional information recording medium 100, anoutput decreases drastically by 12 dB. On the contrary, by theinformation recording medium 1, an output decreases by as low as 2 dB.In other words, by using the information recording medium 1, a crosserase phenomenon is improved by up to 10 dB in comparison with theconventional information recording medium 100 although a dye material isused for the information recording medium 1.

[0116] The information recording medium 1 according to the firstembodiment of the present invention is such an information recordingmedium that is recorded with information on either a groove portion “G”or a land portion “L” of the recording layer 12. It is studied thateither portion is suitable for recording information in view ofreproduction, and it is founded that recording on a land portion “L” ofthe recording layer 12 decreases an error rate and is excellent in arewriting characteristic. In view of that a land portion “L” is disposedin a side closer to the light transmitting layer 11 than a grooveportion “G”, and reproducing light and recording light is irradiated onthe light transmitting layer 11, it is considered that thermal flow of amaterial constituting the recording layers 12 is suppressed to somedegree in an area of land portion “L”.

[0117]FIG. 4 is a cross sectional view of the information recordingmedium 1 according to the first embodiment of the present inventionexhibiting a state of recording and reproducing the recording layer 12.In FIG. 4, a recording apparatus and a reproducing apparatus isillustrated by an objective lens 50 b as a representative of them. Alaser beam 89 is emitted through the objective lens 50 b of therecording apparatus when recording. The laser beam 89 is convergedselectively on a land portion “L” of the microscopic pattern 20 in theinformation recording medium 1 with respect to the horizontal direction.As for the vertical direction, the laser beam 89 is convergedselectively on the recording layer 12 through the light transmittinglayer 11.

[0118] Further, a record mark “M” is recorded on a portion where thelaser beam 89 is converged on. In other words, recording is selectivelyconducted to the recording layer 12 corresponding to a land portion “L”.

[0119] As mentioned above, in the case that the recording layer 12 isformed by a phase change material, the recording hereupon is conductedby change of reflectivity, change of refractive index, or change of bothof them. In the case of being formed by a magneto-optical material, therecording is conducted by change of Kerr rotation angle.

[0120] Further, in the case of a dye material, the recording isconducted by change of refractive index, change of depth, or change ofboth of them.

[0121] On the other hand, when reproducing, a laser beam 99 is emittedthrough the objective lens 50 b of the reproducing apparatus. The laserbeam 99 is converged selectively on a land portion “L” of themicroscopic pattern 21 in the information recording medium 1 withrespect to the horizontal direction.

[0122] Further, with respect to the vertical direction, the laser beam99 is converged selectively on the recording layer 12 through the lighttransmitting layer 11. A record mark “M” is recorded selectively on therecording layer 12 corresponding to a land portion “L”. Consequently, arecord mark “M” can be read out from a portion where the laser beam 99is converged on.

[0123] According to the first embodiment of the present invention, asmentioned above, the microscopic pattern 20 of the information recordingmedium 1 is formed to be P≦λ/NA, wherein “P” is the pitch betweenadjoining two groove portions “G” or land portions “L”, “λ” is awavelength of a laser beam for recording or reproducing, and “NA” is anumerical aperture of an objective lens.

[0124] Further, recording is conducted to either one of a land portion“L” and a groove portion “B”. Consequently, an information recordingmedium recorded in high density can be obtained as well as reducing across erase phenomenon.

[0125] In addition thereto, according to the first embodiment of thepresent invention, an information recording medium that is low in errorrate and excellent in rewriting characteristic can be obtained byrecording selectively on a land portion “L”.

[0126] A method of embedding an auxiliary information such as addressand a reference clock, which is a second object of the informationrecording medium 1 according to the first embodiment of the presentinvention, is explained hereafter. The present invention is explained byspecifying an embodiment in which recording is conducted on a landportion “L” hereupon.

[0127] In case of a recording type information recording medium, it isrequired that recording is accurately conducted in an arbitraryposition, which is requested by a user. If the recording typeinformation recording medium is constituted by arranging a grooveportion “G” and a land portion “L” alternatively as shown in FIG. 2,positioning based on a relative distance between a recording apparatusor reproducing apparatus and the information recording medium can onlybe conducted. Therefore, recording in a required position can not beconducted accurately.

[0128] Accordingly, an address information is essential to be embeddedin somewhere on the microscopic pattern 20. It is considered that analternating configuration of groove portion “G” and land portion “L” asthe same configuration as a commonly known optical disc such as a CD,for example, is transported to a free plane at each certain macroscopicinterval (each interval of the order of milli) and pits having aplurality of lengths are arranged into the free plane. An addressinformation is defined by a combination of the pit length. Reading out apit in such a free plane can be conducted by reading out a depth asphase change that is the same manner as a CD, so that the reading out apit is an easy method. However, providing such a free plane as anaddress area makes losses of recording capacity expands. In view ofreliability of reading out, the loss is approximately 10% and hard to beallowed.

[0129] Furthermore, in the case of the recording type informationrecording medium, a relative speed between an information recordingmedium and a recording apparatus, that is, a recording speed affects arecording density and besides, signal quality. Therefore, a referenceclock for designating a recording speed correctly is essential. In casethat a reference clock is provided in a recording apparatus, a relativespeed can hardly be adjusted even though the relative speed is shiftedby various conditions. Consequently, it is desirable for the referenceclock to be provided inside an information recording medium.Particularly, the information recording medium 1 is in disciform and alinear velocity changes every moment in case of a recording mode by theCLV (Constant Linear Velocity) recording method. Therefore, it isessential for the reference clock to be provided inside the informationrecording medium 1.

[0130] In order to solve the problems and satisfy the requirementsmentioned above, there provided a method for embedding an auxiliaryinformation and a reference clock in the information recording medium 1.An auxiliary information hereupon is a data array that is usedsubsidiarily when recording in the recording layer 12 of the informationrecording medium 1 by a user.

[0131] Actually, an auxiliary information is composed of at least anaddress information. An address information exhibits an address thatchanges continuously by a position of the information recording medium 1and is data selected out from information such as absolute addressallocated to the whole area of the information recording medium 1,relative address allocated to a partial area, track number, sectornumber, frame number, field number, and time information.

[0132] These address data sequentially change in the order of incrementor decrement in accordance with progress of a recording track such as aland portion “L”, for example.

[0133] It is acceptable that an address information can be accompaniedby a specific information, which is composed of a small amount of data.A specific information is common data in the plain of the recordinglayer 12. Such a specific information is at least selected out from, forexample, type of an information recording medium, size of theinformation recording medium, estimated recording capacity of theinformation recording medium, estimated recording linear density of theinformation recording medium, estimated recording linear velocity of theinformation recording medium, track pitch of the information recordingmedium, recording strategic information such as peak power, bottompower, erase power, and pulse period, reproduction laser powerinformation, manufacturer's information, production number, lot numberor batch number, control number, copyright related information, key forciphering, key for deciphering, ciphered data, recording permissioncode, recording refusal code, reproducing permission code, andreproducing refusal code.

[0134] Further, an auxiliary information is such information that, forexample, is described by the decimal number system or the hexadecimalnotation and converted into the binary number system such as a BCD(Binary-Coded Decimal) code and a gray code.

[0135] Furthermore, the auxiliary information can accompany an errorcorrecting code in order to prevent a data error.

[0136] In addition, a reference clock is provided for representing apause of a certain period of time on a signal. Actually, a referenceclock is composed of a single frequency that will be mentioned later.

[0137]FIG. 5 is a plan view showing a structure of the microscopicpattern 20, which is embedded with an auxiliary information and areference clock, of the information recording medium 1 according to thefirst embodiment of the present invention. That is, the microscopicpattern 20 is composed of a land portion “L” and a groove portion “G”.

[0138] Further, the land portion “L” or the groove portion “G” is formedby being wobbled. In other words, both an auxiliary information and areference clock are recorded by a wobbling groove. In FIG. 5, thedrawing is illustrated such that an auxiliary information and areference clock are recorded by wobbling a land portion “L”.

[0139] Furthermore, the microscopic pattern 20 is divided into at leasttwo areas macroscopically, and at least composed of an auxiliaryinformation area 200 and a reference clock area 300. As mentioned above,each of the auxiliary information area 200 and the reference clock area300 is wobbled respectively. By a wobbling groove, an auxiliaryinformation is recorded in the auxiliary information area 200 and areference clock is recorded in the reference clock area 300. These areasare continuously formed without being interrupted, so that continuousreproduction is enabled. FIG. 5 is illustrated such that only two areasof the auxiliary information area 200 and the reference clock area 300are allocated. However, this alternative allocation of the auxiliaryinformation area 200 and the reference clock area 300 is repeated andconstitutes whole area of the microscopic pattern 20 of the informationrecording medium 1.

[0140] Moreover, in FIG. 5, both of the auxiliary information area 200and the reference clock area 300 are formed on the land portion “L” as amost preferable example. How ever, it is essential that one of theauxiliary information area 200 and the reference clock area 300 isformed on a groove portion “G” if the other one of the auxiliaryinformation area 200 and the reference clock area 300 is formed on agroove portion “G”.

[0141] As mentioned above, by forming the auxiliary information area 200and the reference clock area 300 on the same shaped portion, that is, aland portion “L” or a groove portion “G”, an auxiliary information and areference clock can be reproduced continuously.

[0142] The auxiliary information 200 is composed of a waveform that ismodulated digital data hereupon. Actually, the waveform is composed ofany one of an amplitude-shift keying modulation wave 250 (250, 251, and252), a frequency-shift keying modulation wave 260 (260, 261, and 262)and a phase-shift keying modulation wave 270 (270, 271, and 272) or anyone of them that are transformed. FIG. 5 exemplifies particularly thatthe auxiliary information 200 is the frequency-shift keying modulationwaveform 260 (260, 261, and 262).

[0143] Although these modulation methods will be detailed later, in theamplitude-shift keying modulation method, digital data of an auxiliaryinformation are expressed such as “1” or “0” by a fundamental wavewhether or not the fundamental wave is existed. In the case of thefrequency-shift keying modulation method, digital data of an auxiliaryinformation are expressed such as “1” or “0” by a frequency of afundamental wave whether the frequency is higher or lower. In the caseof the phase-shift keying modulation method, digital data of anauxiliary information are expressed such as “1” or “0” by a differenceof phase angular of a fundamental wave. It is possible to record anauxiliary information such as an address more efficiently and toallocate the reference clock area 200 relatively longer by adoptingthese modulation methods. Being able to allocate the reference clockarea 200 longer enables to detect a reference clock for a long period oftime when recording the information recording medium 1, so that stablerecording can be conducted.

[0144] A fundamental wave of these modulation methods hereupon can beselected out from a sinusoidal wave (or cosine wave), a triangular wave,and a rectangular wave. In case that a sinusoidal wave (cosine wave) isselected out from them, a harmonic component can be minimized whenreproducing, and resulted in improving power efficiency and suppressinga jitter. Consequently, a sinusoidal wave (cosine wave) is suitable fora fundamental wave.

[0145] In addition thereto, a signal waveform formed by any of thesemodulation methods is recorded geometrically as a wobbling sidewall ofland portion “L”.

[0146] On the other hand, the reference clock area 300 is composed of asingle-frequency wave 350 that is continuously repeated. Since thefrequency is single, it is possible to generate a frequency in responseto a number of revolutions by making the information recording medium 1move relatively while reproducing. Consequently, a reference clock canbe produced. The reference clock can be used for revolution control whenrecording.

[0147] Further, a fundamental wave having a single frequency is composedof any one of a sinusoidal wave (cosine wave), a triangular wave, and arectangular wave. In case that a sinusoidal wave (cosine wave) isselected out from them, a harmonic component can be minimized whenreproducing, and resulted in improving power efficiency and suppressinga jitter. Consequently, a sinusoidal wave (cosine wave) is suitable fora fundamental wave.

[0148] In addition thereto, a signal waveform formed by any of thesemodulation methods is recorded geometrically as a wobbling sidewall ofland portion “L”.

[0149] As mentioned above, the microscopic pattern 20 according to thepresent invention is at least composed of the auxiliary information area200 and the reference clock area 300. An auxiliary information and areference clock are recorded continuously by a wobbling groove withoutinterruption. These auxiliary information and reference clock recordedon a sidewall of the land portion “L” in a shape of wobbling are readout from a push-pull signal by using a well-known 2-division or4-division detector. Revolution control can be conducted by the read-outreference clock while recording, and further an information can bewritten in or erased from a predetermined address by extracting anaddress information from an auxiliary signal.

[0150] It is desirable for reproduction that the auxiliary informationarea 200 and the reference clock area 300 are in uniform length witheach other and allocated alternately. In case that a length is notuniform with each other, it is not predicted that an auxiliaryinformation such as an address or a reference clock can be detected atwhich timing while reproducing. Consequently, confusions may occur. Onthe contrary, in case that each length is uniform and they are allocatedalternately, arrival of a succeeding signal can be easily predicted oncereproduction is enabled. Accordingly, a timing of obtaining an auxiliaryinformation and a reference clock is predicted by a logic circuit andthe auxiliary information and the reference clock can be reproduced inless error.

[0151] Further, the reference clock area 300 is an important signal forcontrolling a number of revolutions when reproducing the informationrecording medium 1, so that the reference clock area 300 is desirable tobe formed as long as possible. Actually, it is necessary for a ratio ofa length of the reference clock area 300 to a total length of theauxiliary information area 200 and the reference clock area 300 to bemore than 50%, desirably more than 60%. If the ratio is less than thevalue mentioned above, a reference clock can only be obtained for ashort period of time. Consequently, revolution control is conductedintermittently and a reproduction operation becomes unstable. In a worstcase, mismatching occurs in a logic circuit for reproducing and theoperation is resulted in interrupting the reproduction.

[0152] It is acceptable that a shape of fundamental waveform and anamount of amplitude of these two areas are different from each other.However, they are desirable to be the same in view of simplification andstabilization of a recording circuit and a reproducing circuit.

[0153] With respect to a frequency, in case that the auxiliaryinformation area 200 is formed with the amplitude-shift keyingmodulation wave 250 or the phase-shift keying modulation wave 270, it isacceptable that a frequency of the amplitude-shift keying modulationwave 250 or the phase-shift keying modulation wave 270 is different froma frequency of the single-frequency wave 350 of the reference clock area300. However, in case of the same frequency, the recording circuit andthe reproducing circuit can be simplified drastically. Consequently, thesame frequency is desirable. Their frequencies are desirable to be atleast related to “integral multiples” or “one over an integer”.

[0154] Further, in case that an auxiliary information of the auxiliaryinformation area 200 is formed by the frequency-shift keying modulationwave 260, it is acceptable that two frequencies constituting thefrequency-shift keying modulation wave 260 are different from afrequency of the single-frequency wave 350 in the reference clock area300. However, in case that one of the two frequencies constituting thefrequency-shift keying modulation wave 260 is the same as the frequencyof the single-frequency wave 350, a physical length utilized forextracting a clock can be extended slightly. Consequently, the samefrequency is desirable. These three frequencies are desirable to berelated to “integral multiples” or “one over an integer” respectively inview of simplifying a recording circuit and a reproducing circuit.

[0155] Furthermore, it is also acceptable that a start-bit signal, astop-bit signal and a sync signal is recorded as a wobbling groove atthe boundary between the auxiliary information area 200 and thereference clock area 300 in order to clarify the division of them. Withrespect to such a signal, a single-frequency wave having a predeterminedperiod and a predetermined frequency can be used.. However, thepredetermined frequency is essential to be at least different from thefrequency of the single-frequency wave 350 that constitutes thereference clock area 300. It is most desirable that the predeterminedfrequency is different from any frequency constituting thesingle-frequency wave 350, the amplitude-shift keying modulation wave250, the frequency-shift keying modulation wave 260, or the phase-shiftkeying modulation wave 270.

[0156] As mentioned above, the information recording medium 1 accordingto the first embodiment of the present invention can be in any shapesuch as disciform, card and tape. Consequently, the microscopic pattern20 that is composed of approximately parallel grooves can also be in anyshape such as spiral, coaxial and line. In case that the informationrecording medium 1 is in disciform and the microscopic pattern 20 isrecorded spirally, the land portion “L” and the groove portion “G” isrecorded by a recording method such as the constant angular velocity(CAV), the constant linear velocity (CLV), the zone constant angularvelocity (ZCAV) and the zone constant linear velocity (ZCLV) recordingmethods, wherein the ZCAV and the ZCLV recording methods are a methodthat forms zones, which vary by radius, and conducts a differentcontrolling system independent of each zone. In case that theinformation recording medium 1 is recorded by the CLV recording method,for example, a same linear velocity is maintained in the whole area ofthe information recording medium 1.

[0157] Further, in case of recording by the ZCAV recording method, theCLV recording method is conducted in one zone and a controlling systemsimilar to the CAV recording method is conducted in the informationrecording medium 1 totally.

[0158] Furthermore, in case of recording by the ZCLV recording method,the CAV recording method is conducted in one zone and a controllingsystem similar to the CAV recording method is conducted in theinformation recording medium 1 totally.

[0159]FIG. 6 is an enlarged plan view of the reference clock area 300 inthe information recording medium 1 on the basis of recording on a landportion “L” through the CLV recording method. In case that recording isconducted on a portion corresponding to a land portion “L” of therecording layer 12, an auxiliary information or a reference clock isessential to be extracted from the land portion “L”. Consequently, asingle-frequency wave 350 to be a reference clock must be recorded onthe land portion “L”. In view of that recording light scan along acenterline not shown of the land portion “L”, both sidewalls of the landportion “L” are essential to be parallel to each other. In other words,three land portions “L1” through “L3” (hereinafter generically referredto as land portion “L”) and two groove portions “G1” and “G2”(hereinafter generically referred to as groove portion “G”) areillustrated in FIG. 6.

[0160] Further, in FIG. 6, a sidewall of the inner circumferential sideof the land portion “L2” or “L3” is shown as “L2i” or “L3i” (hereinaftergenerically referred to as inner sidewall “Li”) and another sidewall ofthe outer circumferential side of the land portion “L1” or “L2” is shownas “L1o” or “L2o” (hereinafter generically referred to as outer sidewall“Lo”).

[0161] Further, a side wall of the outer circumferential side of thegroove portion “G1” or “G2” is shown as “G1i” or “G2i” (hereinaftergenerically referred to as inner sidewall “Gi”) and another sidewall ofthe outer circumferential side of the groove portion “G1” and “G2” isshown as “G1o” or “G2o” (hereinafter generically referred to as outersidewall “Go”). The inner sidewall “Li” of the land portion “L” and theouter sidewall “Go” of the groove portion “G” represents the same wall,and the outer sidewall “Lo” of the land portion “L” and the innersidewall “Gi” of the groove portion “G” represents the same wallhereupon.

[0162] Furthermore, a reference clock is recorded on the land portion“L” as a sinusoidal-wave signal through the CLV recording method.Therefore, as shown in FIG. 6, three land portions “L1” through “L3” arenot parallel to each other in almost all cases. However, in order toextract a sinusoidal-wave signal accurately with avoiding interferencefrom both sidewalls caused by a phase shift of each sidewall, the innersidewall “Li” and the outer sidewall “Lo” of the land portion “L” areessential to be always formed in parallel to each other. From a point ofview contrary to this, it is represented such that the inner sidewall“Gi” and the outer sidewall “Go” constituting the groove portion “G”,which is the other portion than the land portion “L”, are never inparallel to each other.

[0163]FIG. 7 is an enlarged plan view of the reference clock area 300 inthe information recording medium 1 on the basis of recording on a landportion “” through the CAV recording method. In case that theinformation recording medium 1 is recorded by the CAV recording method,a same angular velocity is maintained in a whole area of the informationrecording medium 1. By this CAV recording method, the wobbling landportion “L” and the groove portion “G” can always be in parallel to eachother completely, so that a crosstalk amount between adjoining groovesbecomes constant at all times. Consequently, ideal reproduction that cansuppress output fluctuation of wobbling frequency and fluctuation in atime axis direction can be conducted. In other words, as shown in FIG.7, each land portion “L” becomes in parallel to each other and at thesame time each groove portion “G” also becomes in parallel to each otherdue to the characteristic of angular velocity. Three land portions “L1”through “L3” (hereinafter generically referred to as land portion “L”)and two groove portions “G1” and “G2” (hereinafter generically referredto as groove portion “G”) are illustrated in FIG. 7. In FIG. 7, asidewall of the inner circumferential side of the land portion “L2” or“L3” is shown as “L2i” or “L3i” (hereinafter generically referred to asinner sidewall “Li”) and another sidewall of the outer circumferentialside of the land portion “L1” or “L2” is shown as “L1o” or “L2o”(hereinafter generically referred to as outer sidewall “Lo”).

[0164] Further, a side wall of the outer circumferential side of thegroove portion “G1” or “G2” is shown as “G1i” or “G2i” (hereinaftergenerically referred to as inner sidewall “Gi”) and another sidewall ofthe outer circumferential side of the groove portion “G1” or “G2” isshown as “G1o” or “G2o” (hereinafter generically referred to as outersidewall “Go”). The inner sidewall “Ai” of the land portion “L” and theouter sidewall “Go” of the groove portion “G” represents the same wall,and the outer sidewall “Lo” of the land portion “L” and the innersidewall “Gi” of the groove portion “B” represents the same wallhereupon.

[0165] As mentioned above, in case of recording on a land portion “L” ofthe recording layer 12, for example, a clock is essential to beextracted from the land portion “L”. Therefore, the single-frequencywave 350 to be a reference clock is recorded on the land portion “L”.The clock is recorded by the CAV recording method, so that the threeland portions “L1” through “L3” are completely in parallel to each otheras shown in FIG. 7. At the same time, the groove portion “G” that is therest portion other than the land portion “L” is also in parallel to eachother perfectly. In other words, in order to extract a sinusoidal-wavesignal accurately, the inner sidewall “Li” and the outer sidewall “Lo”of the land portion “L” are essential to be always formed in parallel toeach other. However, in the case of recording by the CAV recordingmethod, the inner sidewall “Gi” and the outer sidewall “Go” of thegroove portion “G” is also formed to be in parallel to each other.

[0166] In either recording method of the CLV and the CAV, both thesidewalls constituting the land portion “L”, that is, the inner sidewall“Li” and the outer sidewall “Lo” of the land portion “L” are essentialto be in parallel to each other.

[0167] Further, particularly in the case of recording by the CAVrecording method, not only the land portion “L” but also both thesidewalls “Gi” and “Go” constituting the groove portion “G” are inparallel to each other. In other words, the inner sidewall “Li” and theouter sidewall “Lo” of the land portion “L” and the inner sidewall “Gi”and the outer sidewall “Go” of the groove portion “G” are all inparallel to each other.

[0168] The shape of the sidewall of the reference clock area 300 in themicroscopic pattern 20 recorded spirally in the information recordingmedium 1 in disciform is mentioned above. This situation is exactly thesame as for the auxiliary information area 200 due to a similar reasonfor the reference clock area 300. In other words, in either recordingmethod of the CLV and the CAV, both the sidewalls constituting the landportion “L”, that is, both the inner sidewall “Li” and the outersidewall “Lo” of the land portion “L” are essential to be in parallel toeach other.

[0169] In the information recording medium 1 according to the presentinvention, the auxiliary information area 200 and the reference clockarea 300 is continuously formed without interruption, so that bothsidewalls constituting the land portion “L”, that is, the inner sidewall“Li” and the outer sidewall “Lo” of the land portion “L” are formed inparallel to each other in any area on the information recording medium1.

[0170] With referring to FIG. 8, a wobbling amount Δ of a wobblinggroove that is formed in the information recording medium 1 according tothe first embodiment of the present invention is explained next.

[0171]FIG. 8 is an enlarged plan view of the microscopic pattern 20formed by the CLV recording method in the information recording medium 1according to the first embodiment of the present invention. Themicroscopic pattern 20 is composed of the auxiliary information area 200and the reference clock area 300, which are formed with a fundamentalwave based on the sinusoidal wave or the cosine wave and continuewithout interruption. In FIG. 8, a centerline of wobbling groove isshown by a chain line. A distance between two chain lines, which areadjacent to each other, is defined as a pitch “P”.

[0172] Further, the information recording medium 1 shown in FIG. 8 isassumed to be recorded on a land portion “L” and a spot of reproducinglight beam or a recording light beam that focuses on the land portion“L” is shown by a circle in doted line. The spot diameter is exhibitedby “S”, that is equal to “λ/NA”, as mentioned above.

[0173] Furthermore, the land portion “L” wobbles and its wobbling widthΔ in peak to peak value is shown by two doted lines.

[0174] Moreover, in case that the information recording medium 1 is indisciform, a wobbling direction corresponds to a radial direction of thedisc-shaped information recording medium 1.

[0175] A reproducing apparatus of the information recording medium 1 canextract a wobbling amplitude of the auxiliary information area 200 andthe reference clock area 300 as a signal through a reproducing lightspot without interruption. In other words, by producing a push-pullsignal from reflected light of the reproducing light spot, asingle-frequency wave 350, a amplitude-shift keying modulation wave 250,a frequency-shift keying modulation wave 260, or a phase-shift keyingmodulation wave 270, which is based on a sinusoidal wave, can bedirectly extracted as a signal of similar figure. More accurately, atrack direction of wobbling groove is transformed into a time axisdirection, and further a radial direction of the wobbling groove istransformed into an amplitude direction of a reproduced signal, and thenthe single-frequency wave 350, the amplitude-shift keying modulationwave 250, the frequency-shift keying modulation wave 260, or thephase-shift keying modulation wave 270 is reproduced as the signal ofsimilar figure.

[0176] According to another aspect of the present invention, theinformation recording medium 1 of the first embodiment is formed with awobbling groove of which wobbling width Δ is within a range of Δ<P. Incase that the information recording medium 1 is manufactured asmentioned above, adjacent tracks, that is, adjacent land portions “L”,for example, do not contact with each other physically, so thatcrosstalk caused by recording can be avoided.

[0177] Further, the inventors of the present invention make anexperiment on a case that a phase change material is used for therecording layer 12 and recording is conducted by difference ofreflectivity, phase difference, or both of them. In other words, theinventors try to reproduce an auxiliary information through a push-pullsignal detecting method from the information recording medium 1 that isrecorded with random data by conducting a phase change recording method.As a result of the experiment, a limit of enabling to detect anauxiliary information is 0.01S≦Δ. In case of a groove of which wobblingwidth Δ is formed to be less than 0.01S, random data caused by the phasechange recording method are superimposed extremely on an auxiliaryinformation as a noise and an error rate of the auxiliary informationdrastically increases.

[0178] On the contrary, the wobbling width Δ is set to the limitation of0.01S≦Δ, an auxiliary information can be reproduced sufficiently even ina low reflectivity condition such as an amorphous state due to the phasechange recording method. However, in case of 0.15S<Δ, a jitter in timeaxis direction occurs in an auxiliary information signal and a referenceclock signal due to an affection of reproduction crosstalk caused by anadjacent groove, particularly, stability of the reference clock signalis deteriorated.

[0179] Accordingly, a relation between the wobbling width Δ and thepitch P shall be Δ<P, particularly, conditions satisfying relations Δ<Pand 0.01S≦Δ≦0.15S are most suitable for forming a wobbling groove.

[0180]FIG. 9 is an enlarged plan view of the microscopic pattern 20 ofthe information recording medium 1, wherein recording is conducted onthe recording layer 12 of the information recording medium 1 shown inFIG. 8. In FIG. 9, a record mark M is recorded on the land portions “L”that are wobbled. The record mark M represents whether a modulatedsignal is ON or OFF. There provided various lengths of record mark M asit will be explained later. As mentioned above, the record mark M isformed on the recording layer 12. In case that the recording layer 12 isformed by a phase change material, a record mark M is recorded byreflectivity and phase difference, difference of reflectivity, or phasedifference.

[0181] A structure of how a shape of wobbling groove is reflected to adifferential signal is complemented hereupon.

[0182]FIG. 10 is an enlarged plan view of a photo-detector 9 thatcollects reproducing light, which is irradiated on the informationrecording medium 1 and reflected. In case that the photo-detector 9 is a4-division detector, as shown in FIG. 10, the detector 9 is divided intofour elements in accordance with the radial direction and the tangentialdirection of the information recording medium 1. A push-pull signal canbe produced by subtracting each sum signal in the tangential direction.More accurately, with defining that the four elements are A, B, C, and Drespectively, and further defining that electric currents, which areobtained from each of the elements A, B, C, and D when they receivelight, are Ia, Ib, Ic and Id respectively, the push-pull signal can berepresented by an equation “(Ia+Ib)−(Ic+Id)”. In other words, a signalto be obtained is a differential signal in the radial direction. When areproducing apparatus of the information recording medium 1 traces acenter of groove, that is, the center of the chain line shown in FIGS. 8and 9, the push-pull signal is in a form of obtaining an outputdifference in the radial direction with respect to the centerline.Consequently, a wobbling shape can be reproduced as a signal thatreflects the wobbling shape.

[0183] The total constitution of the information recording medium 1according to the first embodiment of the present invention is detailedabove.

[0184] Further, it is acceptable that the auxiliary information area 200is conducted with not only recording on a sidewall by selecting onemodulation wave out of the amplitude-shift keying modulation wave 250,the frequency-shift keying modulation wave 260, and the phase-shiftkeying modulation wave 270 but also time-division recording on eachsidewall in different areas by selecting two or three modulationmethods.

[0185] A single-frequency wave can be superimposed on theamplitude-shift keying modulation wave 250, the frequency-shift keyingmodulation wave 260, or the phase-shift keying modulation wave 270. Inother words, with respect to the amplitude-shift keying modulation wave250 and the frequency-shift keying modulation wave 260, a wave having asame frequency as a frequency that constitutes those modulation waves ora different frequency from frequencies of those modulation waves can besuperimposed and recorded.

[0186] Particularly, with respect to the frequency-shift keyingmodulation wave 260, a wave having either a higher frequency or a lowerfrequency of the frequency-shift keying modulation wave 260 can besuperimposed on the frequency-shift keying modulation wave 260.Similarly, a wave having a frequency of “an integer multiple” or “oneover an integer” of either a higher frequency or a lower frequency ofthe frequency-shift keying modulation wave 260 can be superimposed onthe frequency-shift keying modulation wave 260.

[0187] Further, with respect to the phase-shift keying modulation wave270, a wave having a frequency of “an integer multiple” or “one over aninteger” of the frequency constituting the phase-shift keying modulationwave 270 can be superimposed on the phase-shift keying modulation wave270.

[0188] In any case, by using a well-known band pass filter or phasedetector, it is possible to separate a single-frequency wave and any ofthe amplitude-shift keying modulation wave 250, the frequency-shiftkeying modulation wave 260, and the phase-shift keying modulation wave270 from the superimposed wave. For example, an experience is conductedwith respect to the phase-shift keying modulation wave 270. It isconfirmed that a single-frequency wave and a phase-shift keyingmodulation wave can be separated as far as an amplitude ratio of thephase-shift keying modulation wave to the single-frequency wave iswithin a predetermined range of 1:5 to 5:1 while superimposing thesingle-frequency wave on the phase-shift keying modulation wave. Inother words, in case that an information recording medium ismanufactured as a trial by setting the amplitude ratio for out of thepredetermined range, one wave having larger amplitude can be reproduced.However, the other wave having smaller amplitude can not be reproduceddue to an excessively low signal to noise ratio (S/N).

[0189] In case of such a constitution that a single-frequency wave to besuperimposed and the single-frequency wave 350 of the reference clockarea 300 is the same frequency, a reference clock can also be extractedform the auxiliary information area 200. Consequently, such aconstitution is more suitable for recording by superimposing. That is tosay, since a reference clock continues substantially although theauxiliary information area 200 is formed over a long distance, extremelystable recording can be conducted.

[0190] It is acceptable that an auxiliary information to be formed on asidewall of a land portion “L” is highly discomposed and recorded withdistributed. By combining with dummy data “101”, for example,distributed recording is one recording method such that an auxiliaryinformation is recorded as a data array such as “101X”, wherein X iseither “0” or “1”, and the data array is allocated in each predeterminedinterval.

[0191]FIG. 11 is a first example showing a distributed recording of anauxiliary information. As shown in FIG. 11, the dummy data “101” as adata trigger “Tr” is allocated in the predetermined interval, at every11 bits herein, and an “X” is allocated in succession to the datatrigger “Tr”. In other words, by extracting only the “X” allocatedimmediately after the data trigger “Tr”, an auxiliary information can berestored. In this case, with defining that the “1” is data, theauxiliary information shown in FIG. 11 can be restored as a series ofdata that are composed of existing data (Data), none data (None) andexisting data (Data) in sequence, so that “101” can be reproduced as theauxiliary information. This recording method is effective for a formatthat is allowed to read a data array to be processed with spending alonger period of time. It is defined hereupon that one-bit data to beextracted at each predetermined interval is a “word” and an auxiliaryinformation is constituted by integrating a plurality of “words”.

[0192] Further, a variation of the recording method shown in FIG. 11 isexhibited in FIG. 12.

[0193]FIG. 12 is a second example showing a distributed recording of anauxiliary information. As shown in FIG. 12, a data trigger “Tr” and data“X” can be allocated with separating them in a predetermined bit ofinterval. In FIG. 12, the data trigger “Tr” is “11” and allocated atevery 11 bits. Data are recorded by “101” whether the “101” is existedor not in a predetermined interval. In other words, by extracting dataexisting in the fourth bit to the sixth bit, one-bit data can berestored. In this second example, data can be restored as a series ofdata composed of existing data (Data), none data (None) and existingdata (Data) in sequence, so that “101” is reproduced as the auxiliaryinformation. This recording method is effective for reducing erraticreadout because the data “X” is separated from the data trigger “Tr”.

[0194] Furthermore, with respect to a third example of the highlydistributed recording method, a first specific data pattern such as “11”is allocated or recorded at every predetermined interval. Then, a secondspecific data pattern such as “101” is allocated between the firstspecific patterns. A position at where the second specific pattern isallocated is advanced by a predetermined bit, distance or period withrespect to the first specific data pattern. Particularly, two positionsare allocated previously.

[0195]FIG. 13 is a third example of the highly distributed recordingmethod showing a distributed recording of an auxiliary information. Asshown in FIG. 13, a data trigger “Tr” or “11”, is allocated at everypredetermined interval, actually every 11 bits hereupon, as the firstspecific data pattern, and a second specific data pattern “101” isallocated between the data triggers “Tr” or “11”. A position at wherethe second specific data pattern is allocated is provided with twopositions; one is within a range of the third bit to the fifth bit fromthe data trigger “Tr” or “11” and the other is within a range of thefifth bit to the seventh bit. Decoding is conducted by judging that thesecond specific data pattern is allocated in either position. In thecase of FIG. 13, the second specific data pattern “101” is sequentiallyallocated in the positions starting with the third bit, fifth bit andthird bit respectively, so that data or words “101” can be reproduced asan auxiliary information. This recording method is effective forensuring higher reliability to an auxiliary information because therecording method can add a parameter whether or not the data “101” canbe read out to one of standards for judging reliability.

[0196] In other words, data to be recorded in an auxiliary informationarea are at least composed of a data trigger that is allocated at everypredetermined interval and data allocated at a predetermined positionbetween the data triggers. The information recording medium 1 accordingto the present invention is recorded with an auxiliary information by arelative distance between the data trigger and the data or the secondspecific data pattern.

[0197] In the description of the third example of the highly distributedrecording method mentioned above, the method of distributed recordingthat is conducted by using a position difference between the firstspecific data pattern and the second specific data pattern is explained.However, in case that a pattern, which is extremely high in readoutaccuracy, can be provided, it is acceptable for both the first specificdata pattern and the second specific data pattern that their patternsare the same pattern. In other words, decoding can be conducted byextracting a specific pattern having a shorter time interval from aspecific data pattern recorded at a predetermined time interval and bymeasuring a distance interval or the time interval between the specificdata pattern and the specific pattern. With referring to FIG. 14,further details are explained next.

[0198]FIG. 14 is a fourth example showing a distributed recording of anauxiliary information. As shown in FIG. 14, a data trigger “Tr” or “11”is allocated at a predetermined interval, at every 11 bits hereupon, asa first specific data pattern, and a second specific data pattern “11”having the same pattern as the data trigger “Tr” is allocated betweenthe data triggers “Tr”. A position at where the second specific datapattern is allocated is provided with two positions; one is within arange of the third bit to the fifth bit from the data trigger “Tr” or“11” and the other is within a range of the fifth bit to the seventhbit. Decoding is conducted by judging that the second specific datapattern is allocated in either position. In the case of FIG. 14, thesecond specific data pattern “11” is sequentially allocated in thepositions starting with the third bit, fifth bit and third bitrespectively, so that data or words “101” can be reproduced as anauxiliary information. This recording method is advantageous to areproducing circuit to be simplified because the recording methodrequires only one specific data pattern.

[0199] The highly distributed recording method is explained above infour types. According to these highly distributed recording methods, anauxiliary information is recorded as data that are decomposed into everyone bit. Actually, some bits of dummy data are prepared for a datatrigger “Tr” first, and a data array composed of continuing single datasuch as continuing zeros, for example, is prepared next. The datatrigger “Tr” is connected with the single data array so as to beallocated at every predetermined interval for the data trigger “Tr”.Then, the auxiliary information that is decomposed into every one bit isrecorded so as to convert a part of the single data array by apredetermined rule. In other words, an auxiliary information is recordedby converting data allocated in a bit, which is advanced by apredetermined distance from the data trigger “Tr”, by the predeterminedrule.

[0200] On the other hand, when reproducing the auxiliary information,all data are once read out from a sidewall of land portion “L” as a dataarray and a data trigger “Tr” that is allocated at every predeterminedinterval is detected from the data array. Then, one bit of data that isequivalent to a “Word” shown in FIGS. 11 to 14 is extracted from thedata array excluding the data trigger “Tr” with referring to thepredetermined rule. The auxiliary information is restored by integratingthe detected one-bit data.

[0201] The methods for recording in highly distributed and forreproducing an information recording medium according to the presentinvention are explained above. In case of an auxiliary information,particularly, an address information, a plurality of zeros or ones maycontinue, so that there is existed a possibility of generating a DCcomponent in a data array being read out. In order to eliminate such apossibility, it is acceptable that the data array is previouslymodulated by the base-band modulation method and recorded. In otherwords, there existed a method such that a data array to be recorded on asidewall of land portion “L” by wobbling modulation is previouslyreplaced with another codes so as to reduce a sequence of zeros and onesto a certain number or less. With respect to such a method, the methodsuch as Manchester code, PE (phase encoding) modulation, MFM (modifiedfrequency modulation), M2 (Miller squared) modulation, NRZI (non returnto zero inverted) modulation, NRZ (non return to zero) modulation, RZ(return to zero) modulation and differential modulation can be usedindependently or by combining some of them together.

[0202]FIG. 15 is a table exhibiting data change before and aftermodulating a base-band.

[0203] With respect to a base-band modulation method, which is mostsuitable for the information recording medium 1 of the presentinvention, there is provided the Manchester code (biphase modulation)method. The Manchester code method is a method of applying two bits toeach one bit of an original data to be recorded as shown in FIG. 15.That is, “00” or “11” is assigned to a data “0” to be recorded, and “01”or “10” to a data “1”.

[0204] Further, an inverted code of inverting a last code of precedingdata is essentially applied to a head code of succeeding data whenarranging the succeeding data after the preceding data.

[0205]FIG. 16 is a table exhibiting an example of actual data changebefore and after modulating a base-band. As shown in FIG. 16, anoriginal data “100001” is assigned to be a code array of “010011001101”.The original data contains a sequence of four “0”s and is anasymmetrical data in which an appearing probability of “0” is twice thatof “1”. If such an asymmetrical data is modulated by the Manchester codemethod, a sequence of “0” or “1” is only two maximally and the originaldata is converted into a symmetrical data having equal appearingprobability of “0” and “1”. As mentioned above, the base-bandmodulation, which restricts a sequence of same bits within a certainquantity, is effective to increase stability of reading out data.Consequently, the base-band modulation method is suitable forpre-treatment for a long array of auxiliary information.

[0206] An amplitude-shift keying modulation wave 250 (250, 251 and 252),a frequency-shift keying modulation wave 260 (260, 261 and 262) and aphase-shift keying modulation wave 270 (270, 271 and 272), which areused for the information recording medium 1 according to the embodimentone of the present invention as a wobbling groove modulation wave, areexplained next.

[0207] With referring to FIGS. 17 through 19, the amplitude-shift keyingmodulation waves 250, 251 and 252 are depicted.

[0208]FIG. 17 shows a first example of an amplitude-shift keyingmodulation waveform according to the present invention. FIG. 18 shows asecond example of an amplitude-shift keying modulation waveformaccording to the present invention. FIG. 19 shows a third example of anamplitude-shift keying modulation waveform according to the presentinvention.

[0209] As shown in FIG. 17, the amplitude-shift keying modulation wave250 according to the present invention is geometrically recorded bymodulating data through the amplitude-shift keying modulation method andactually, constituted by an amplitude section 2501 and a non-amplitudesection 2500, wherein the amplitude section 2501 is formed by wobbling agroove in a predetermined period. In other words, the amplitude section2501 is a wobbling part of groove and the non-amplitude section 2500 isa non-wobbling part of groove.

[0210] Further, the amplitude section 2501 and the non-amplitude section2500 is corresponding to “1” and “0” of a data bit respectively. Theamplitude section 2501 is composed of a plurality of waves that continuemore than one cycle hereupon. A number of waves is not limited to aspecific cycle. However, if it is too many, length of the non-amplitudesection 2500 consequently becomes longer and resulting in that afundamental wave, which produces a gate when reproducing, is hardlydetected. Therefore, two to one hundred cycles, preferably three tothirty cycles are suitable for the number of waves of the amplitudesection 2501. As mentioned above, digital data (in case of FIG. 17, itis “10110”) is recorded by whether or not amplitude is existed. Thepush-pull signal detecting method mentioned above can be used forreading out the recorded data.

[0211] Furthermore, it should be understood that the amplitude-shiftkeying modulation wave 250 according to the present invention does notlimit each length or each amplitude size of the amplitude section 2501and the non-amplitude section 2500 to specific figure. In the case ofthe amplitude-shift keying modulation wave 250 shown in FIG. 17, thelength of the amplitude section 2501 is set to be longer than that ofthe non-amplitude section 2500.

[0212] In FIG. 18, an amplitude-shift keying modulation wave 251 isconstituted by amplitude sections 2511 a through 2511 c andnon-amplitude sections 2511. Each amplitude of the amplitude sections2511 a through 2511 c is unequal to each other. However, unequalamplitude is acceptable for the amplitude-shift keying modulationmethod.

[0213] Further, it is also acceptable that assigning each amplitude inmultiple levels intentionally realizes recording in multi-values morethan three values.

[0214] Furthermore, in case of an amplitude-shift keying modulation wave252 shown in FIG. 19, each amplitude of amplitude sections 2521 is equalto each other and each length of the amplitude sections 2521 is equal tothat of non-amplitude sections 2520. This configuration is alsoacceptable for the amplitude-shift keying modulation method.Particularly, in case that data are recorded in digital by the binaryvalue of “0” and “1”, an isotropic layout as shown in FIG. 19 isdesirable for the digital recording by the binary value. In other words,if each height of the amplitude sections 2521 is made equal to eachother and each length of the amplitude sections 2521 is made equal tothat of the non-amplitude sections 2520, judging “0” or “1” whenreproducing can be realized by sufficient threshold value of amplitude.

[0215] Moreover, data arranged in series can be read out by onethreshold value of time, so that a reproducing circuit can besimplified.

[0216] In addition thereto, even in case that jitter exists inreproduced data, there is existed a merit that influence of the jittercan be minimized.

[0217] Further, with assuming that a code to be recorded is ideallysymmetrical, total length of the amplitude sections 2521 is made equalto that of the non-amplitude sections 2520 and resulted in that no DCcomponent is existed in a reproduced signal. It is advantageous todigital recording that no DC component releases a burden on datadecoding and servo.

[0218] As mentioned above, by using any of the amplitude-shift keyingmodulation waves 250, 251 and 252, an auxiliary information is recordedin an information recording medium 1 according to the first embodimentof the present invention. Either “0” or “1” is recorded in response towhether a wobble is existed on a sidewall of groove or not, so thatability of judging “0” or “1” is excellent. In other words, a low errorrate can be obtained although an auxiliary information is in relativelylow C/N (carrier to noise ratio).

[0219] Further, although recording on the recording layer 12 isconducted by a user, influence of random noise caused by the recordingcan be reduced and a low error rate can be maintained.

[0220] With referring to FIGS. 20 through 22, frequency-shift keyingmodulation waves 260 through 262 are explained next.

[0221]FIG. 20 shows a first example of a frequency-shift keyingmodulation waveform according to the present invention. FIG. 21 shows asecond example of a frequency-shift keying modulation waveform accordingto the present invention. FIG. 22 shows a third example of afrequency-shift keying modulation waveform according to the presentinvention.

[0222] A frequency-shift keying modulation wave is for recording datageometrically by the frequency-shift keying modulation method and iscomposed of a plurality of sections that are formed by wobbling groovesby different frequencies. Actually, in the case of binary data, thefrequency-shift keying modulation wave is geometrically recorded byusing a higher frequency section and a lower frequency section. In caseof multi-valued data such as “n” values, a frequency-shift keyingmodulation wave is geometrically recorded by the frequency-shift keyingmodulation method that uses “n” kinds of frequency sections. Hereinafterthe examples are explained with assuming that data to be recorded are inbinary. FIG. 20 is one example of recording data “10110” geometrically.In FIG. 20, the frequency-shift keying modulation wave 260 is composedof three higher frequency sections 2601 and two lower frequency sections2600. The higher frequency section 2601 and the lower frequency section2600 are equivalent to “1” and “0” of a data bit respectively and theyare recorded in digital by changing the frequency at each one channelbit. A number of waves that constitute each frequency section is notlimited to one specific number. Each frequency section is composed of awave that continues more than one cycle. However, in consideration ofthat data are not redundant too much in a reproducing apparatus so as todetect a frequency accurately and to obtain a certain degree of datatransfer rate, each frequency section, which is corresponding to eachdata bit mentioned above, is desirable to be constituted by a number ofwaves within a range of one cycle to one hundred cycles, preferably onecycle to thirty cycles.

[0223] Further, it is acceptable that each amplitude of the higherfrequency section 2601 and the lower frequency section 2600 is equal toeach other. However, an amplitude ratio is not limited to one specificfigure. Amplitude of the higher frequency section 2601 can be formedlarger than that of the lower frequency section 2600 in consideration ofa frequency response of reproducing apparatus.

[0224] Furthermore, the push-pull signal detecting method mentionedabove can be used for reading out the recorded data.

[0225] It should be understood that the information recording medium 1according to the first embodiment of the present invention does notplace a restraint on physical length or amplitude size of a channel bit,which is composed of the higher frequency section 2601 and the lowerfrequency section 2600. For example, in FIG. 20, the physical length oflower frequency section 2600 is designated to be longer than that of thehigher frequency section 2601.

[0226] As shown in FIG. 21, in case of a frequency-shift keyingmodulation wave 261, it is acceptable that amplitude of a higherfrequency section 2611 and a lower frequency section 2610 are equal toeach other and length of the higher frequency section 2611 is equal tothat of the lower frequency section 2610. By equalizing each amplitudeand length as mentioned above, judging “0” or “1” can be conducted bysufficient threshold value of amplitude when reproducing.

[0227] Further, data arranged in series can be read out by one thresholdvalue of time, so that a reproducing circuit can be simplified.

[0228] Furthermore, in case that jitter exists in reproduced data, thereis existed a merit that influence of the jitter can be minimized.

[0229] Moreover, with assuming that a code to be recorded is ideallysymmetrical, total length of the higher frequency sections 2611 is equalto that of the lower frequency sections 2610 and resulted in that no DCcomponent is existed in a reproduced signal. It is advantageous todigital recording that no DC component releases a burden on datadecoding and servo.

[0230] In FIGS. 20 and 21, the higher frequency section 2601 or 2611 andthe lower frequency section 2600 or 2610 is connected to each otherrespectively, wherein each waveform rises at a point where a channel bitchanges. However, phase jump happens in probability of 50% at the momentwhen a channel bit changes. Consequently, a high frequency component isgenerated and resulted in deterioration of power efficiency per eachfrequency.

[0231] In order to eliminate such phase jump, a frequency-shift keyingmodulation wave 262 is provided. In FIG. 22, the frequency-shift keyingmodulation wave 262 is composed of a higher frequency section 2621 r or2621 f (hereinafter referred generically to as higher frequency section2621) and a lower frequency section 2620. The higher frequency section2621 and the lower frequency section 2620 is arranged so as to maintainphase continuity at a point where each channel bit of thefrequency-shift keying modulation wave 262 changes over. Actually, astarting phase of the lower frequency section 2620 is selected so as tobe that a phase direction of the end of the higher frequency section2621 and a phase direction of the start of the lower frequency section2620 are the same direction.

[0232] Further, the reverse connection is the same as such that astarting phase of the higher frequency section 2621 is selected so as tobe that a phase direction of the end of the lower frequency section 2620and a phase direction of the start of the higher frequency section 2621are the same direction. If the starting phase is selected as mentionedabove, continuity of phase is maintained and power efficiency isimproved.

[0233] Furthermore, a reproduction envelope becomes constant, so that adata error rate of auxiliary information, which is recorded in theinformation recording medium 1, is improved. Such a method ofmaintaining continuity of phase at a point where a channel bit changescan be applied to the auxiliary information area 200 and the referenceclock area 300 shown in FIG. 5. A data error rate of auxiliaryinformation is further improved if waveforms of the auxiliaryinformation area 200 and the reference clock area 300 are arranged asmentioned above.

[0234] A frequency of the higher frequency section 2621 (2601, 2611 or2621) and the lower frequency section 2620 (2600, 2610 or 2620) isarbitrary selected. However, in order to eliminate interference with afrequency range that is provided for recording data on the informationrecording medium 1 by a user, it is strictly required for the higherfrequency section 2621 not to be extremely high frequency in comparisonwith a frequency of the lower frequency section 2620.

[0235] On the other hand, in order to improve a reproduction error rateof address data, a frequency difference between the higher frequencysection 2621 and the lower frequency section 2620 shall be kept incertain degree so as to maintain excellent separativeness. From theseviewpoints, a frequency ratio of the higher frequency section 2621 tothe lower frequency section 2620 is desirable to be within a range of1.05 to 5.0, particularly, desirable to be within a range of 1.09 to1.67. In other words, phase relation between two frequencies isdesirable to be within a range of 2π±(π/20.5) to 2π±(π/0.75),particularly, desirable to be within a range of 2π±(π/12) to 2π±(π/2),that is, 360±15 degrees to 360±90 degrees, wherein the reference phaseis defined as 2π.

[0236] With respect to a frequency ratio (ratio of higher frequency tolower frequency), if the frequency ratio shown in FIG. 22 is assigned tobe 1.5, there exists a phase relation between these higher and lowerfrequencies such that the higher frequency is shifted by −π/2.5 from areference phase of a single-frequency wave and the lower frequency isshifted by +π/2.5 from the reference phase of the single-frequency wave,wherein the phase relation becomes 2π±(π/2.5) when the reference phaseis defined as 2π. In other words, the phase relation is shifted to360±72 degrees. It is expressed that these two frequencies are integralmultiple (wherein it is three times and two times respectively) of thefrequency (in this case 0.5) of the single-frequency wave. Consequently,it is advantageous for a demodulation circuit to be simplified.

[0237] Further, generating a clock signal becomes easier by using acircuit having a window of 0.5.

[0238] Furthermore, a synchronous detector circuit can conductdemodulation. In this case, an error rate can be reduced extremely.

[0239] As mentioned above, an auxiliary information is recorded in theinformation recording medium 1 of the present invention by thefrequency-shift keying modulation waves 260, 261 and 262. The binarydata “0” or “1” is recorded in accordance with change of a wobblingfrequency, so that ability of judging “0” or “1” is excellent. In otherwords, an auxiliary information can be obtained in a low error ratealthough a C/N is relatively low.

[0240] More, influence of random noise caused by recording on therecording layer 12 by a user can be reduced and a low error rate can bemaintained.

[0241] With referring to FIGS. 23 through 25, phase-shift keyingmodulation waves 270, 271 and 272 are explained next.

[0242]FIG. 23 shows a first example of a phase-shift keying modulationwaveform according to the present invention. FIG. 24 shows a secondexample of a phase-shift keying modulation waveform according to thepresent invention. FIG. 25 shows a third example of a phase-shift keyingmodulation waveform according to the present invention.

[0243] As shown in FIG. 23, the phase-shift keying modulation wave 270is formed by recording data geometrically by the phase-shift keyingmodulation method. Actually, the phase-shift keying modulation wave 270is composed of a plurality of sections, which are constituted bywobbling a groove by a predetermined frequency. In the case of binarydata, the phase-shift keying modulation wave 270 is composed of anadvancing phase section 2701 and a receding phase section 2700. In caseof multi-valued data such as “n” values, a phase-shift keying modulationwave is composed of “n” phase sections, which correspond to “n” kinds ofphases respectively. Hereinafter the examples are explained withassuming that data to be recorded are in binary. FIG. 23 is one exampleof recording data “10110” geometrically. In FIG. 23, the phase-shiftkeying modulation wave 270 is composed of three advancing phase sections2701 and two receding phase sections 2700. The advancing phase section2701 and the receding phase section 2700 are equivalent to “1” and “0”of a data bit respectively, and recorded in digital by changing thephase at each one channel bit. Actually, the advancing phase section2701 and the receding phase section 2700 are exhibited by a sinusoidalwave of “sin 0” and another sinusoidal wave of “sin(−π)” respectively.As shown in FIG. 23, the advancing phase section 2701 and the recedingphase section 2700 are constituted by one cycle of waveformrespectively. However, phase difference between them is as many as π, sothat they can be separated and reproduced sufficiently by the envelopedetection method or the synchronous detection method.

[0244] Each frequency of the advancing phase section 2701 and thereceding phase section 2700 is identical to each other. A number ofwaves, which constitutes the advancing phase section 2701 and thereceding phase section 2700, is not restricted to a specific number.Both phase sections are composed of a wave that continues more than onecycle. However, in consideration of that data are not redundant too muchin a reproducing apparatus so as to detect a frequency accurately and toobtain a certain degree of data transfer rate, each phase sectioncorresponding to each data bit that is mentioned above is desirable tobe constituted by a number of waves within a range of one cycle to onehundred cycles, preferably one cycle to thirty cycles.

[0245] It is acceptable for each physical length of the advancing phasesection 2701 and the receding phase section 2700 to be identical or not.In case that each physical length is identical, data, which are combinedin series, can be divided into piece by a predetermined time, that is, apredetermined clock when reproducing. Consequently, a reproductioncircuit can be simplified.

[0246] Further, in case that jitter exists in reproduced data, there isexisted a merit that enables to minimize influence of the jitter.

[0247] It is also acceptable for each amplitude of the advancing phasesection 2701 and the receding phase section 2700 to be coincide witheach other or not. However, in consideration of easier reproduction, itis desirable for the advancing phase section 2701 and the receding phasesection 2700 that each amplitude of them coincides with each other.

[0248] The information recording medium 1 according to the firstembodiment of the present invention can deal with not only binary databut also multi-valued data. Dealing with how many kinds of phasesdepends on that phase difference of each data bit can be separated intowhat degree of resolution. The limit of separation of the informationrecording medium 1 is obtained experimentally by the inventors of thepresent invention and it is confirmed that phase difference can beseparated into up to π/8. In other words, various phase sections, whichconstitute the multi-valued channel bit, can deal with minimum phasedifference of each phase section within a range of π/8 to π, wherein πis equivalent to minimum phase difference of a binary data. That is tosay, a wide range of data from binary to hexadecimal can be dealt with.

[0249]FIG. 24 is a second example showing a phase-shift keyingmodulation wave 271 that is recorded with 4-valued data. In FIG. 24 thephase-shift keying modulation wave 271 is composed of a first phase[sin(−3π/4)] section 2710, a second phase [sin(−π/4)] section 2711, athird phase [sin(π/4)] section 2712 and a fourth phase [sin(3π/4)]section 2713. Minimum phase difference of each phase section is π/2, sothat each of the 4-valued data can be sufficiently separated andobtained. Hereupon, the first phase section 2710, the second phasesection 2711, the third phase section 2712 and the fourth phase section2713 are corresponded to data “1”, “2”, “3” and “4” respectively forconvenience.

[0250] When recording multi-valued data such as mentioned above, themulti-valued data can be replaced by multidimensional data. Withassuming that the data is two-dimensional data (x, y), for example, thedata “1” through “4” can be replaced by data (0, 0), data (0, 1), data(1, 0), and data (1, 1) respectively.

[0251]FIG. 25 is a third example showing a phase-shift keying modulationwave 272, which deals with binary data in the information recordingmedium 1 according to the first embodiment of the present invention. InFIG. 25, a fundamental wave is a saw-tooth wave and the waveform isasymmetrical for rising and falling sections. By controlling the risingand falling sections individually, difference of phase is exhibited. Inthe case of the waveform shown in FIG. 25, data “1” is recorded as asection 2721 of which a wave rises gradually and falls rapidly(hereinafter referred to as a rapidly falling section 2721), and data“0” as a section 2720, which rises rapidly and falls gradually(hereinafter referred to as a rapidly rising section 2720). In case thataddress data “10110” is recorded, for example, as shown in FIG. 25, thephase-shift keying modulation wave 272 is geometrically recorded withthe rapidly falling section 2721, the rapidly rising section 2720, therapidly falling section 2721, the rapidly falling section 2721 and therapidly rising section 2720 in order. Such a recording method thatrecords data by angle difference between a rising angle and a fallingangle can demodulate the data by inputting the data into a high-passfilter and by extracting a differential component. Consequently, therecording method is advantageous to the data that can be reproduced evenunder low C/N condition.

[0252] As mentioned above, an auxiliary information is recorded in theinformation recording medium 1 according to the first embodiment of thepresent invention by the phase-shift keying modulation wave 270, 271 or272. The binary data “0” or “1” is recorded in accordance with phasechange of a number of wobbles, so that ability of judging “0” or “1” isexcellent. Particularly, a frequency of the phase-shift keyingmodulation method is constant. Therefore, a filter, which is installedin a preceding stage of a demodulation circuit for auxiliaryinformation, can be assigned to be a band-pass filter of which passingband is specialized in one frequency.

[0253] Further, the band-pass filter can also eliminate any kind ofnoises including a noise that is caused by recording by a usereffectively. In other words, a lower error rate can be obtained eventhough a C/N is relatively low.

[0254] Furthermore, influence of random noise caused by the recordingcan be effectively eliminated and a low error rate can be maintained,even though recording in the recording layer 12 of the informationrecording medium 1 is conducted by a user.

[0255] As mentioned above, constitutions and effects of theamplitude-shift keying modulation waves 250, 251 and 252, thefrequency-shift keying modulation waves 260, 261 and 262 and thephase-shift keying modulation waves 270, 271 and 272 according to thepresent invention are depicted. In the above-mentioned descriptions thatare explained with referring to FIGS. 17 through 25, they are explainedas examples with defining that a fundamental wave is a sinusoidal waveand recorded. However, it is also acceptable that a fundamental wave isdefined as a cosine wave and recorded.

[0256] The constitution and the effect of the information recordingmedium 1 according to the first embodiment of the present invention isdetailed above. However, the inventive concept of the present inventionis not limited to the information recording medium 1 that is describedwith referring to FIGS. 1 though 25. It is apparent that many changes,modifications and variations in the arrangement of equipment and devicesand in materials can be made without departing from the inventionconcept disclosed herein.

[0257] Further, in the above-mentioned first embodiment, eachconstituting component can be replaced by each other or exchanged byanother component that is disclosed herein.

[0258] For example, the shape of the information recording medium 1 isnot restricted to one specific shape, any shape such as disc, card andtape can be applied for the information recording medium 1. It is alsoapplicable for the information recording medium 1 to be a shape incircular, rectangular or elliptic.

[0259] In addition, an information recording medium having a hole isalso acceptable.

[0260]FIG. 26 shows a first example of disk-shaped information recordingmedium 1 having a hole. FIG. 27 shows a second example of card-shapedinformation recording medium 1A having no hole. FIG. 28 shows a thirdexample of a card-shaped information recording medium 1B having a hole.In FIG. 26, the disc-shaped information recording medium 1 is formedwith a microscopic pattern 20, which is constituted by a continuoussubstance of approximately parallel grooves in a circular arc and inparallel with the inner or outer circumference of the informationrecording medium 1. The form of the microscopic pattern 20 is notlimited to be the circular arc. Any form that is arranged continuouslyin 360 degrees coaxially or spirally is also acceptable. In FIG. 27, thecard-shaped information recording medium 1A having no hole is formedwith a microscopic pattern 20, which is constituted by a continuoussubstance of approximately parallel grooves linearly and in parallelwith the longitudinal direction of the information recording medium 1A.In FIG. 28, the card-shaped information recording medium 1B having ahole is formed with a microscopic pattern 20, which is constituted by acontinuous substance of approximately parallel grooves in circular.

[0261] Further, the cross section of the information recording medium 1explained by using FIG. 1 is not limited to the cross sectional viewshown in FIG. 1. It is apparent that the invention concept of thepresent invention can apply to an information recording medium havingvarious cross sectional configurations.

[0262] [Second Embodiment]

[0263]FIG. 29 is a cross sectional view of an information recordingmedium according to a second embodiment of the present invention. InFIG. 29, an information recording medium 2 is identical to theinformation recording medium 1 shown in FIG. 1 except for the lighttransmitting layer 11, so that details of the same components will beomitted. As shown in FIG. 29, the light transmitting layer 11 of theinformation recording medium 1 is divided into two layers; a lighttransmitting layer 11 a and an adhesive light transmitting layer 11 b,wherein the light transmitting layer 11 a is similar to the lighttransmitting layer 11 as mentioned above. The adhesive lighttransmitting layer 11 b is a layer for adhering the light transmittinglayer 11 a on the recording layer 12 firmly, and transmits more than 70%of light having a wavelength λ, desirably more than 80%.

[0264] With respect to a material of the adhesive light transmittinglayer 11 a, an adhesive or cohesive resin such as thermosetting resins,various energy ray curable resins including UV ray curable resins,visible radiation curable resins and electron beam curable resins,moisture curable resins, plural liquid mixture curable resins andthermoplastic resins containing solvent can be used.

[0265] Further, a thickness of the adhesive light transmitting layer 11b is more than 0.001 mm as a minimum thickness exhibiting adhesiveness,desirably less than 0.04 mm in view of preventing a growth of stresscrack, and more desirably to be more than 0.001 mm and less than 0.03mm. Desirably further more, the thickness is more than 0.001 and lessthan 0.02 mm. However, it is the most desirable that the thickness ismore than 0.001 mm and less than 0.01 mm in view of warpage of theinformation recording medium 2 totally.

[0266] [Third Embodiment]

[0267]FIG. 30 is a cross sectional view of an information recordingmedium according to a third embodiment of the present invention. In FIG.30, an information recording medium 3 is identical to the informationrecording medium 1 shown in FIG. 1 except for the substrate 13, so thatdetails of the same components will be omitted. As shown in FIG. 30, thesubstrate 13 shown in FIG. 1 is replace with a substance of two-layerstructure; a substrate 13 a and a resin layer 14.

[0268] With respect to a material of the resin layer 14, such resins asthermosetting resins, various energy ray curable resins including UV raycurable resins, visible radiation curable resins and electron beamcurable resins, moisture curable resins, plural liquid mixture curableresins and thermoplastic resins containing solvent can be used.Reproducing light never reaches to the resin layer 14, so that there isexisted no limitation in transmittance.

[0269] Further, a thickness of the resin layer 14 is desirable to beless than 0.02 mm in view of warpage of the information recording medium3 totally.

[0270] [Fourth Embodiment]

[0271]FIG. 31 is a cross sectional view of an information recordingmedium according to a fourth embodiment of the present invention. InFIG. 31, an information recording medium 4 is identical to theinformation recording medium 1 shown in FIG. 1 except for the lighttransmitting layer 11 and the substrate 13, so that details of the samecomponents will be omitted. As shown in FIG. 31, the light transmittinglayer 11 of the information recording medium 1 is divided into twolayers; a light transmitting layer 11 a and an adhesive lighttransmitting layer 11 b as same constitution as those of the informationrecording medium 2 shown in FIG. 29.

[0272] Further, the substrate 13 shown in FIG. 1 is replace with asubstance of two-layer structure; a flat substrate 13 b and a patterntransferring layer 15 having a microscopic pattern 22, wherein thepattern transferring layer 15 is an extremely thin film for having themicroscopic pattern 22.

[0273] Furthermore, a material of the pattern transferring layer 15 isselected out from a metal, an alloy of the metal and a resin, wherein analloy includes a compound such as oxide, nitride, carbide, sulfide andfluoride, and its thickness is designated to be within a range of 5 nmto 200 nm.

[0274] With respect to a typical example of resin, there is existednovolac light-sensitive resin and polyhydroxy styrene light-sensitiveresin, wherein both resins can be developed by alkali.

[0275] Each component of the information recording mediums 1 through 4shown in FIGS. 1 through 4 and 26 through 31 can be replaced by orcombined with other component mutually as far as a reproductioncharacteristic is not deteriorated.

[0276] For example, it is acceptable to stick two information recordingmediums out of the information recording mediums 1 through 4, whereinone information recording medium is stuck on the other informationrecording medium with facing each substrate 13 (13 a, 13 b) towards eachother.

[0277] Further, one set of the recording layer 12 and the lighttransmitting layer 11 can be stuck on the light transmitting layer 11 ofthe information recording mediums 1 through 4. By this configuration,capacity of the information recording mediums 1 through 4 can beincreased almost twice.

[0278] Furthermore, it is acceptable that laminating a plurality of setsof the recording layer 12 and the light transmitting layer 11 repeatedlyforms a multi-layered information recording medium having a plurality ofrecording layers.

[0279] Further, the information recording mediums 1 through 4 accordingto the first through fourth embodiment of the present invention can beformed with commonly known layers such as an antistatic layer, alubricative layer and a hard coat layer that are laminated on the lighttransmitting layer 11 (or 11 a) although they are not shown in drawings.

[0280] With respect to an actual material for the antistatic layer, aresin such as energy ray curable resin and thermosetting resin that aredispersed with surface-active agent and conductive fine particles can beused.

[0281] With respect to an actual material for the lubricative layer,liquid lubricant of which surface energy is adjusted by modifyinghydrocarbon macromolecule with silicon and fluorine can be used. Athickness of the lubricative layer is desirable to be within a range of0.1 nm to 10 nm approximately.

[0282] Further, with respect to an actual material for the hard coatlayer, a resin, which transmits more than 70% of light having wavelengthλ, such as thermosetting resins, various energy ray curable resinsincluding UV ray curable resins, visible radiation curable resins andelectron beam curable resins, moisture curable resins, plural liquidmixture curable resins and thermoplastic resins containing solvent canbe used.

[0283] Furthermore, the hard coat layer is desirable to exceed a certainvalue of the “scratch test by pencil” regulated by the JapaneseIndustrial Standard (JIS) K5400 in consideration of abrasion resistanceof the light transmitting layer 11 (or 11 a). In consideration of thatglass is a hardest material for an objective lens of a reproducingapparatus of information recording medium, a value of the “scratch testby pencil” for the hard coat layer is most preferable to be more thanthe “H” grade. If the test value is less than the “H” grade, dust thatis caused by scraping the hard coat layer is remarkably generated andresulted in deteriorating an error rate abruptly.

[0284] Moreover, a thickness of the hard coat layer is desirable to bemore than 0.001 mm in consideration of shock resistance. However, thethickness is more desirable to be less than 0.01 mm in consideration ofeach warp of the information recording mediums 1 through 4 totally.

[0285] Further, a thin film, which transmits more than 70% of lighthaving a wavelength λ and has a value of the “scratch test by pencil” ofmore than the “H” grade, can be used for the hard coat layer. Withrespect to an actual example of the thin film, an element such ascarbon, molybdenum and silicon, and their alloy including compositionsuch as oxide, nitride, sulfide, fluoride and carbide can be used. Afilm thickness of such a thin film is desirable to be within a range of1 nm to 1000 nm.

[0286] Furthermore, a label printing can be applied on the outer surfaceof the substrate 13 (13 a, 13 b) opposite to the recording layer 12although the label printing is not shown in any drawings. Various energyray curable resins containing pigment and dye such as UV ray curableresins, visible radiation curable resins and electron beam curableresins can be used suitably for the label printing. A thickness of thelabel printing is desirable to be more than 0.001 mm in consideration ofvisibility of the printing, more desirable to be less than 0.05 mm inconsideration of each warp of the information recording mediums 1through 4 totally.

[0287] A cross sectional surface of a groove portion “G” and a landportion “L” in the microscopic patterns 20, 21 and 22 is formed flatrespectively. However, a cross sectional surface is not limited to flat.Cross-sectionally, they can be formed in a shape of a V-letter or aninverse V-letter.

[0288] Further, any of the information recording mediums 1, 2, 3 and 4can be formed with a read-only area on the plane of the informationrecording medium other than a predetermined area for recording, that is,an area for recording and reproducing. The read-only area can be formedby a pit or a wobbling groove recorded with at least one modulation waveselected out from the amplitude-shift keying modulation wave 250, thefrequency-shift keying modulation wave 260 and the phase-shift keyingmodulation wave 270 on a sidewall of the groove. The informationrecording medium can be provided with the reference clock area 300together with the read-only area hereupon. These read-only area andreference clock area 300 can be formed by a bar code. The read-only areacan provide information for tuning a recording apparatus or areproducing apparatus when recording or reproducing.

[0289] Furthermore, the read-only area can handle an identificationinformation, a copyright information and a copy restriction informationof an individual information recording medium.

[0290] Moreover, the read-only area can be allocated arbitrarily.However, in case of an information recording medium in disciform, it isconsidered that a read-only area and a recording and reproducing area isallocated in the inner circumference area and the outer circumferencearea respectively, and these areas are formed so as not to overlap witheach other. Particularly, it is most desirable that these two areas comeinto contact with each other, and they are connected at one point andresulted in enabling to be reproduced continuously.

[0291] A hologram and a visible microscopic pattern for identifying theinformation recording medium 1, 2, 3 or 4 can be formed in an area otherthan a predetermined area for recording.

[0292] In order to improve ability of loading an information recordingmedium into a reproducing apparatus or a recording apparatus, and inorder to improve protectiveness while loading and handling theinformation recording medium, each of the information recording mediums1 through 4 can be contained in a cartridge.

[0293] In case that the information recording mediums 1 through 4 are indisciform, its dimensions are not limited to one dimension.

[0294] For example, in the case of diameter, various diameters from 20mm to 400 mm can be applied for the information recording mediums 1through 4. Any diameter such as 30, 32, 35, 41, 51, 60, 65, 80, 88, 120,130, 200, 300 and 356 mm can be acceptable.

[0295] The recording layer 12 provided in the information recordingmediums 1 through 4 are shown as a single layer in the respectivedrawings. However, the recording layers 12 can be formed by a pluralityof thin film materials for a purpose of improving recording andreproducing characteristics and storage stability.

[0296] With referring to FIG. 32, another embodiment of informationrecording medium is detailed next.

[0297] [Fifth Embodiment]

[0298]FIG. 32 is a cross sectional view of an information recordingmedium according to a fifth embodiment of the present invention. In FIG.32, an information recording medium 5 is similar to the informationrecording medium 1 of the first embodiment shown in FIG. 1, so that thesame composition or configuration as that of the information recordingmedium 1 is marked by the same symbol as the information recordingmedium 1 and its detail is omitted. As shown in FIG. 32, the informationrecording medium 5 according to the fifth embodiment of the presentinvention is composed of a reflective layer 121, a first protectivelayer 122, a recording layer 123, a second protective layer 124, and alight transmitting layer 11, which are sequentially formed on asubstrate 13 having a microscopic pattern 20 in order.

[0299] With respect to a material for the reflective layer 121, thereexisted a metal having light reflectiveness such as Al, Au and Ag, analloy that contains the metal as a main component and an additiveelement composed of more than one metal, semiconductor or semimetal, anda mixture of metal such as Al, Au and Ag with metal compound such asmetal nitride, metal oxide and metal chalcogenide. Such a metal as Al,Au or Ag and an alloy containing the metal as the main component is highin light reflectiveness and thermal conductivity, so that they arepreferable for the material of the reflective layer 121.

[0300] Further, the reflective layer 121 plays a role of optimizingconduction of heat when recording is conducted to the recording layer123, so that the reflective layer 121 can be called a heat-sink layer.

[0301] With respect to the alloy mentioned above, there existed an alloycomposed of Al or Ag added with at least one element out of Si, Mg, Cu,Pd, Ti, Cr, Hf, Ta, Nb, Mn, Pd, Zr and Rh as an additive element withina range of more than 1 atomic % to less than 5 atomic % in total orcomposed of Au added with at least one element out of Cr, Ag, Cu, Pd, Ptand Ni as an additive element within a range of more than 1 atomic % toless than 20 atomic % in total.

[0302] Particularly, as anti-corrosiveness is excellent and an iterativecharacteristic is improved, the reflective layer 121 is desirable to beconstituted by any one of Al—Cr alloy, Al—Ti alloy, Al—Ta alloy, Al—Zralloy, Al—Ti—Cr alloy and Al—Si—Mn alloy, which contain Al as a maincomponent and an additive element that is designated to be within arange of more than 0.5 atomic % to less than 3 atomic %. With respect tothe additive element, adding a metal or a semiconductor to a base metalalone makes a crystal particle smaller and results in reducing noiselevel while reproducing, so that adding additive element is desirable.

[0303] Furthermore, adding additive element is effective for improvingstability under a high temperature and high humidity condition. Alloyssuch as Al—Ti, Al—Cr, Al—Zr, Al—Si, Ag—Pd—Cu and Ag—Rh—Cu, for example,are desirable for the material of the reflective layer 121. In case ofutilizing a violaceous semiconductor laser, constituting the reflectivelayer 121 by an alloy of Al system or Ag system can obtain higherreflectivity. A thickness of the reflective layer 121 is within a rangeof 10 nm to 300 nm.

[0304] More, the thickness of the reflective layer 121 varies by adegree of thermal conductivity of a metal or an alloy constituting thereflective layer 121. In case of Al—Cr alloy, for example, thermalconductivity decreases in accordance with content of Cr that increases.Consequently, the thickness of the reflective layer 121 must be madethicker; otherwise increasing content of Cr does not comply withrecording strategy. In case that content of Cr is larger, the reflectivelayer 121 is hard to be heated or cooled down and becomes a so-calledgradually cooling structure. In order to control forming a record markin accordance with the recording strategy, some consideration such thatshortening a head pulse, shortening multi-pulses or extending a coolingpulse is required. In case that the thickness of the reflective layer121 exceeds 50 nm, the reflective layer 121 does not change optically oraffect a value of reflectivity. However, affection to a cooling speedincreases extremely. In case of increasing the thickness of thereflective layer 121 to more than 300 nm, it takes extra time whilemanufacturing an information recording medium. Consequently, it isdesirable for the film thickness of the reflective layer 121 to besuppressed possibly by using a material having higher reflectivity.

[0305] Moreover, by dividing the reflective layer 121 into more than twolayers, a noise level while reproducing an information recording mediumcan be reduced. Such a reflective layer 121 composed of more than twolayers is formed as follows. In case of forming the reflective layer 121having a thickness of 150 nm in total by using a single disc sputteringsystem, which forms each layer on a substrate 13 in a plurality ofvacuum chambers while transporting the substrate 13 one by one, a firstreflective layer is formed by a first material in a first vacuum chamberat a filming speed of 2 nm/s, and then second and third reflectivelayers are formed in second and third vacuum chambers respectively at afilming speed of 6.5 nm/s. Consequently, a plurality of the substrates13 (discs) can be filmed one after another in a short period of time aslong as 10 seconds. By the above-mentioned process, a crystal particlecan be made finer by changing a filming speed.

[0306] Accordingly, a noise level can be reduced when reproducing theinformation recording medium 5.

[0307] The first protective layer 122 and the second protective layer124 is effective for protecting the substrate 13 and the recording layer123 from deformation and resulting in deteriorating a recordingcharacteristic by excessive heat while recording, for preventingoxidization of recording materials, and effective for improving a signalcontrast by an optical interference effect while reproducing.

[0308] Further, these first and second protective layers 122 and 124 aretransparent at a wavelength of a light beam for recording andreproducing and its refractive index “n” is within a range of 1.9≦n≦2.5.

[0309] Furthermore, both the first protective layer 122 and the secondprotective layer 124 are not required to be made by same material andcomposition. It is acceptable to be constituted by different materials.A thickness of the second protective layer 124 decides a wavelengthexhibiting a minimum value of spectral reflectance.

[0310] Moreover, the first protective layer 122 and the secondprotective layer 124 is further effective for activating crystallizationof a recording layer and for improving an erase ratio.

[0311] With respect to a material of these first and second protectivelayers 122 and 124, there is provided an inorganic thin film such asZnS, SiO₂, silicon nitride, and aluminum oxide.

[0312] Particularly, an oxidized thin film of metal or semiconductorsuch as Si, Ge, Al, Ti, Zr and Ta, a nitride thin film of metal orsemiconductor such as Si, Ge and Al, a carbide thin film of metal orsemiconductor such as Ti, Zr, Hf and Si, a sulfide thin film of metal orsemiconductor such as ZnS, In₂S₃, TaS₄ and GeS₂ and a film of mixturecompound containing more than two compounds out of the above-mentionedcompounds such as oxide, nitride, carbide and sulfide are desirable forthe first and second protective layers 122 and 124 because they are highin heat resistance and chemically stable.

[0313] Further, with respect to a material of the first and secondprotective layers 122 and 124, it is desirable that the material doesnot diffuse into the recording layer 123. Compounds of oxide, sulfide,nitride and carbide are not necessary to be a stoichiometricalcomposition. Controlling a composition and using them by mixing are alsoeffective for controlling a refractive index. By changing a contentamount of oxygen, sulfur, nitrogen and carbon, a refractive index “n” iscontrolled. If a content amount of them increases, a refractive index“n” decreases. A mixture film of ZnS and SiO₂ is particularly desirablefor a material of the first and second protective layers 122 and 124,because recording sensitivity, C/N (carrier to noise ratio), and anerase ratio is hard to be deteriorated by a plurality of repetitions ofrecording and reproducing. A thickness of the first protective layer 122and the second protective layer 124 is within a range of 10 nm to 500 nmrespectively. Particularly, a thickness of the first protective layer122 is desirable to be within a range of 10 nm to 50 nm because ofexcellent recording characteristics such as C/N and erase ratio andenabling to rewrite stably a plurality of times. If a thickness of thesecond protective layer 122 is thinner, a reflectivity increases and arecording sensitivity results in being deteriorated.

[0314] Furthermore, the thinner first protective layer 122 makes a spacebetween the second protective layer 122 and the reflective layer 121narrower and the recording layer 123 results in a so-called rapidcooling construction, so that a relatively large recording power isnecessary for forming a record mark.

[0315] On the contrary, if the thickness of second protective layer 122becomes thicker, the space between the protective layer 122 and thereflective layer 121 becomes wider and the recording layer 123 becomesthe gradually cooling structure. Consequently, a rewriting performanceis deteriorated and a number of repetitions of overwriting decreases. Afilm thickness of the first protective layer 122 is preferable to bethinner than that of the second protective layer 124 and to beconstituted in the rapid cooling construction so as to relief thermaldamage. Consequently, the film thickness of the first protective layer122 is preferable to be within a range of 2 nm to 50 nm. Desirably, afilming speed of the first protective layer 122 is made slower than thatof the second protective layer 124.

[0316] Accordingly, an increase of jitter caused by rewriting issuppressed and a number of repetitions of overwriting increases.

[0317] With respect to a material of the recording layer 123, the samephase change material as the recording layer 12 mentioned above is used.A film thickness of the recording layer 123 is within a range of 5 nm to100 nm, desirably, 10 nm to 30 nm in order to increase a reproducedsignal.

[0318] The same material as the first protective layer 122 is used forthe second protective layer 124. A thickness of the second protectivelayer 124 is within a range of 10 nm to 200 nm. Desirably, the thicknessis within a range of 40 nm to 150 nm to increase a reproduced signalalthough an optimum film thickness varies by a wavelength of a lightsource to be utilized. In case that recording light is a violaceouslaser having a wavelength of 400 nm approximately, modulation amplitudecan be increased by adjusting the thickness to be within a range of 40nm to 60 nm.

[0319] According to the present invention, as mentioned above, therecording characteristics and the reproducing characteristics of theinformation recording medium 5 is improved in addition to the effectsrealized by the information recording medium 1. The laminatedconstitution of the information recording medium 5 can be applied fornot only the information recording medium 1 but also the informationrecording mediums 2 through 4.

[0320] Further, in order to improve the recording characteristics andthe reproducing characteristics more, an auxiliary thin film can beformed on a surface of each layer or between layers.

[0321] The information recording mediums 1 through 5 according to thefirst through fifth embodiment of the present invention are explainedabove. With referring to FIG. 33, a first reproducing apparatus forreproducing any of the information recording mediums 1 through 5 isexplained next. The information recording medium 1 represents theinformation recording mediums 1 though 5 generically for simplifying theexplanation hereinafter.

[0322]FIG. 33 is a block diagram of a first reproducing apparatus forreproducing an information recording medium according to the presentinvention. As shown in FIG. 33, a first reproducing apparatus 40 is anapparatus for reproducing a recording layer 12 of the informationrecording medium 1 and composed of at least a reproducing unit providedwith a light emitting element, which emits reproducing light having awavelength λ of 350 nm to 450 nm and has a noise level of less than RIN−125 dB/Hz, and an objective lens having a numerical aperture NA of 0.75to 0.9, and a control unit, which controls the reproducing unit so as toreproduce the information recording medium 1 by irradiating thereproducing light only on a land portion “L” of the informationrecording medium 1.

[0323] Actually, the first apparatus 40 is at least composed of a pickup50 for reading reflected light from the information recording medium 1,a motor 51 that rotates the information recording medium 1, a servocontroller 52 for controlling to drive the pickup 50 and the motor 51, aturntable 53 for supporting the information recording medium 1 whilerotating, a demodulator 54 for demodulating an information signal thatis read out by the pickup 50, an interface (I/F) 55 for outputting asignal that is demodulated by the demodulator 54, and a controller 60that controls the first reproducing apparatus 40 totally.

[0324] The demodulator 54 hereupon is a digital converter that returns16-bit data to original 8-bit data if a reproduced signal is modulatedby the EFM plus modulation (8-16 modulation) method, which is commonlyused for the DVD system.

[0325] The turntable 53 and the information recording medium 1 isconnected with plugging a center hole Q of the information recordingmedium 1 with the turntable 53. Such a connection between the turntable53 and the information recording medium 1 can be either a fixedconnection or semi-fixed connection, which can load or release theinformation recording medium 1 freely.

[0326] Further, the information recording medium 1 can be contained in acartridge. With respect to a cartridge, a commonly known cartridgehaving an opening and closing mechanism in the center can be used as itis.

[0327] The motor 51 is linked to the turntable 53 and the turntable 53is plugged with the center hole Q of the information recording medium 1.

[0328] Further, the motor 51 supports the information recording medium 1and supplies relative motion for reproduction to the informationrecording medium 1 through the turntable 53. A signal output can besupplied to a not shown external output terminal or directly supplied toa not shown display device, audio equipment or printing equipment.

[0329] The pickup 50 is at least composed of a light emitting element 50a, which emits light having a single wavelength λ within a range of 350nm to 450 nm, desirably 400 nm to 435 nm, an objective lens 50 b havinga numerical aperture NA within a range of 0.75 to 0.9, and a photodetector 9, which receives reflected light that is reflected by theinformation recording medium 1 although they are not shown in FIG. 33.

[0330] Further, the pickup 50 forms reproducing light 99 in conjunctionwith these components. It is acceptable that the light emitting element50 a is a semiconductor laser of gallium nitride system compound or alaser having a second harmonic generating element.

[0331] Furthermore, the servo controller 52 is indicated only one inFIG. 33. However, it can be divided into two; one is a driving controlservo for the pickup 50 and the other is another driving control servofor the motor 51.

[0332] With respect to the demodulator 54, a commonly know equalizer andthe PRML (partial response maximum likelihood) decoding circuit, whichare not shown, can be installed in the demodulator 54. With respect toan equalizer (waveform equalizer), for example, a so-called neural netequalizer (that is disclosed in the Japanese Patent No. 2797035) inwhich a plurality of conversion systems having a nonlinear input-outputcharacteristic is combined together with applying individual variableweighting and constitutes a neural network, a so-called limit equalizer(that is disclosed in the Japanese Patent Application Laid-openPublication No. 11-25998511999) in which an amplitude level ofreproduced signal is limited to a predetermined value and forwarded to afiltering process, and a so-called error selection type equalizer (thatis disclosed in the Japanese Patent Application Laid-open PublicationNo. 2001-110146) in which an error between a reproduced signal and anobjective value for waveform equalization is obtained and a frequency ofthe waveform equalizer is changed adaptively so as to minimize the errorcan be preferably used.

[0333] Moreover, in the commonly known PRML decoding circuit hatcontains a predicted value controlling and equalization errorcalculating circuit, a so-called adaptive viterbi decoder (that isdisclosed in the Japanese Patent Application Laid-open Publications No.2000-228064 and No. 2001-186027) in which a predicted value utilized fordecoding viterbi algorithm is calculated and a frequency response isoptimized so as to minimize an equalization error of waveform equalizercan be used particularly.

[0334] Operations of the first apparatus 40 are explained next. Thereproducing light 99 is emitted from the light emitting element 50 a ofthe pickup 50 through the objective lens 50 b and converged on themicroscopic pattern 21 of the information recording medium 1 loaded onthe turntable 53.

[0335] Accurately, the reproducing light 99 is focused on themicroscopic pattern 21 that is disposed at a depth of 0.07 mm to 0.12 mmcorresponding to the thickness of the light transmitting layer 11.Succeedingly, the reproducing light 99 tracks either a groove portion“G” or a land portion “L”. The tracking is conducted on a predeterminedportion of either the groove portion “G” or the land portion “L”.However, as mentioned above, selecting the land portion “L” is mostdesirable.

[0336] The reflected light from the microscopic pattern 21 is receivedby the photo detector 9 not shown and a recorded signal is read out. Asshown in FIG. 10, the photo detector 9 is divided into four sections. Atotal sum signal, that is, “(Ia+Ib+Ic+Id)” of outputs from the dividedfour sections of the photo detector 9 (hereinafter referred to as“4-division photo detector” 9) is transmitted to the demodulator 54.Reading out the recorded signal is conducted by reproducing a recordmark “M” that is recorded only on the land portion “L”, for example, inthe microscopic pattern 21 as shown in FIG. 3.

[0337] It is omitted in the above explanation that a focus error signalis necessary for focusing to be generated and a tracking error signal isnecessary for tracking to be generated. Such a focus error signal and atracking error signal is generated by a differential signal in theradial direction, that is, “(Ia+Ib)−(Ic+Id)”, which is outputted fromthe 4-division photo detector 9, and transmitted to the servo controller52. In the servo controller 52, a focus servo signal or a tracking servosignal is produced from the received focus error signal or the trackingerror signal in accordance with controlling by the controller 60, thenthe focus servo signal or the tracking servo signal is transmitted tothe pickup 50.

[0338] In addition thereto, a rotary servo signal is produced in theservo controller 52 and transmitted to the motor 51.

[0339] Further, in the demodulator 54, the recorded signal isdemodulated and applied with error correction as required, and a datastream that is obtained is transmitted to the I/F 55. Finally, a signalis outputted externally in accordance with controlling by the controller60.

[0340] As mentioned above, the first reproducing apparatus 40 of hepresent invention is loaded with an information recording medium 1 anddesigned for coping with the reproducing light 99, which is generated bythe light emitting element 50 a (not shown) having single wavelength λwithin the range of 350 nm to 450 nm, the objective lens 50 b (notshown) having the numerical aperture NA of 0.75 to 0.9 and the4-division photo detector 9 (not shown). Therefore, the firstreproducing apparatus 40 can reproduce the information recording medium1 excellently.

[0341] Accordingly, the first reproducing apparatus 40 is such areproducing apparatus that reads out information recorded on therecording layer 12 (or 123). Particularly, the first reproducingapparatus 40 can reproduce contents, which are continuously recorded fora long period of time, and can be used for reproducing an HDTV programand a movie, which are recorded by video equipment, for example.

[0342] With referring to FIG. 34, a second reproducing apparatus forreproducing any of the information recording mediums 1 through 5according to the present invention is explained, wherein the informationrecording medium 1 represents the information recording mediums 1 though6 generically for simplifying the explanation hereinafter.

[0343]FIG. 34 is a block diagram of a second reproducing apparatus forreproducing an information recording medium according to the presentinvention. In FIG. 34, a second reproducing apparatus 41 is identical tothe first reproducing apparatus 40 except for an auxiliary informationdemodulator 56 and a reference clock demodulator 57, which are providedbetween the pickup 50 and the controller 60 and demodulate an auxiliaryinformation and a reference clock read out by the pickup 50respectively. The second reproducing apparatus 41 is a reproducingapparatus that is used for index reproduction of a HDTV program and amovie, which are recorded by video equipment, and for index reproductionof data stored in a computer.

[0344] As mentioned above, a signal that is transmitted from the pickup50 to the demodulator 54 is the total sum signal, that is,“(Ia+Ib+Ic+Id)” outputted form the 4-division photo detector 9 notshown. In addition, another signal that is transmitted from the pickup50 to the auxiliary information demodulator 56 is the differentialsignal in the radial direction, that is, “(Ia+Ib)−(Ic+Id)” outputtedfrom the 4-division photo detector 9 not shown.

[0345] An auxiliary information and a reference clock recordedgeometrically in the information recording medium 1 as a wobblinggroove. The wobbling is formed in the radial direction, so that theauxiliary information and the reference clock can be extracted bymonitoring the differential signal.

[0346] With respect to an actual constitution of the auxiliaryinformation demodulator 56, it is constituted by at least any one of anamplitude-shift keying modulation demodulator, a frequency-shift keyingmodulation demodulator and a phase-shift keying modulation demodulator.

[0347] More accurately, an envelope detector circuit can be suitablyused for the amplitude-shift keying modulation demodulator. A frequencydetector circuit and a synchronous detector circuit can be suitably usedfor the frequency-shift keying modulation demodulator. A synchronousdetector circuit, a delay detector circuit and an envelope detectorcircuit can be suitably used for the phase-shift keying modulationdemodulator.

[0348] The amplitude-shift keying modulation wave 250, thefrequency-shift keying modulation wave 260 or the phase-shift keyingmodulation wave 270, which constitutes the auxiliary signal area 200, isinputted to the auxiliary information demodulator 56 and an auxiliaryinformation is demodulated from the differential signal in the radialdirection outputted from the 4-division photo detector 9.

[0349] The total sum signal may leak into the differential signal in theradial direction although it may be a small amount. In order to avoidsuch leaking, a band-pass filter that is adjusted for a frequency rangeof an auxiliary signal can be inserted between the pickup 50 and theauxiliary information demodulator 56.

[0350] An actual constitution of the reference clock demodulator 57 isat least composed of a slicing circuit. The single-frequency wave 350,which constitutes the reference clock area 300 and is extracted from thedifferential signal in the radial direction that is outputted from the4-division photo detector 9, is inputted to the reference clockdemodulator 57. In the reference clock demodulator 57, thesingle-frequency wave 350 is properly sliced and formed in binary coded.In order to separate the single-frequency wave 350 from a signalobtained from the auxiliary signal area 200, a band pass filter can beinserted into a previous stage immediately before the reference clockdemodulator 57. A binary coded signal controls revolution of the motor51 through the controller 60 and the servo controller 52 in order todecide a number of revolutions of the turntable 53.

[0351] Further, in order to amplify, wave-transform, wave-shape orfrequency-divide the binary coded signal, an amplifier, a waveformtransformer, a waveform shaper, or a frequency divider can be connectedto the second reproducing apparatus 41 additionally.

[0352] The auxiliary information demodulator 56 and the reference clockdemodulator 57 is connected so as to distribute the differential signalrespectively. A switching circuit not shown can be inserted in aprevious stage before the auxiliary information demodulator 56 and thereference clock demodulator 57 in order not to deteriorate S/N and inorder to reduce reading out error. In case that the auxiliaryinformation area 200 and the reference clock area 300 is allocated atevery predetermined interval, prediction for a following signal to beread out can be theoretically decided by reading out and identifying thesignal. Consequently, the switching circuit can be constituted.

[0353] Furthermore, in case that a start bit signal and a stop bitsignal is allocated between the auxiliary information area 200 and thereference clock area 300, prediction for a following signal to be readout can be theoretically decided by referring to these start bit andstop bit signals. Consequently, the switching circuit can betheoretically constituted.

[0354] With referring to FIGS. 34 and 35, an operation of the secondreproducing apparatus 41 is explained next.

[0355]FIG. 35 is a flow chart showing a method for reproducing accordingto an embodiment of the present invention. As shown in FIG. 35, anoperation of the second reproducing apparatus 41, that is, a method ofreproducing the information recording medium 1 by using the secondreproducing apparatus 41 is composed of at least following steps. Theinformation recording medium 1 is loaded on the turntable 53 of thesecond reproducing apparatus 41 (step P1). The reproducing light 99 fromthe pickup 50 is converged and focused on the microscopic pattern 21formed in the information recording medium 1 (step P2), and is madetracking (step P3). A differential signal is produced from reflectedreproducing light 99 that is reflected by the microscopic pattern 21(step P4). A reference clock signal is extracted from the differentialsignal (step P5). Revolution of the motor 51 is controlled by theextracted reference clock signal (step P6). An auxiliary information isextracted from the differential signal (step P7). An address informationis extracted from the extracted auxiliary information (step P8). Aposition of the pickup 51 is controlled by the extracted addressinformation and an address information inputted externally (step P9). Atotal sum signal is demodulated and reproduced (step P10).

[0356] More specifically, the information recording medium 1 is loadedon the turntable 53, which can control revolution of the informationrecording medium 1 to the circumferential direction (the step P1).Succeedingly, the reproducing light 99 is emitted from the lightemitting element 50 a of the pickup 50 through the objective lens 50 band converged on the microscopic pattern 21 of the information recordingmedium 1 (the step P2). Accurately, the reproducing light 99 is focusedon the microscopic pattern 21, which is disposed at a depth of 0.07 mmto 0.12 mm that is equivalent to the thickness of the light transmittinglayer 11. Then, the reproducing light 99 is conducted to a track eitherthe groove portion “G” or the land portion “L” (the step P3). Thetracking is conducted by selecting a portion previously decided.However, as mentioned above, selecting the land portion “L” is mostpreferable. The differential signal “(Ia+Ib)−(Ic+Id)” in the radialdirection is produced from reflected light that is reflected by themicroscopic pattern 21 and picked up by the pickup 50 (the step P4). Theproduced differential signal is transmitted to the reference clockdemodulator 57 and a clock signal is produced (the step P5).

[0357] Further, the clock signal is transmitted to the controller 60 soas to control a number of revolutions of the turntable 53 and controlsrevolution of the motor 51 by way of the servo controller 52 (the stepP6).

[0358] The differential signal is transmitted to the auxiliaryinformation demodulator 56 at the same time, and an auxiliaryinformation is read out (the step P7). At this moment, an addressinformation out of various auxiliary information is extracted from theextracted auxiliary information (the step P8). The extracted addressinformation is compared with another address information that isutilized for indexing data inputted to the controller 60. In case thatthe extracted address information does not coincide with the otheraddress information, the controller 60 sends a signal to the servocontroller 52 and instructs the servo controller 52 to search. Thesearching is conducted such that a number of revolutions of the motor 51is reset to a specific number of revolutions, which corresponds to aradius between the motor 51 and the pickup 50, according to movement inthe radial direction of the pickup 50 while scanning the movement of thepickup 50 in the radial direction.

[0359] Furthermore, during a process of scanning, an address informationoutputted from the address information demodulator 56, which receivesthe differential signal from the pickup 50, is compared with apredetermined address information. The searching is continued until theycoincide with each other (the step P9). When they coincide, scanning inthe radial direction is interrupted and reproduction is switched over tocontinuous reproduction of the total sum signal “(Ia+Ib+Ic+Id)” (thestep P10). An output from the demodulator 54 in which the total sumsignal “(Ia+Ib+Ic+Id)” is inputted, is resulted in demodulating a datastream that is obtained by indexing, and the output is inputted to theI/F 55. Finally, the I/F 55 outputs a signal externally in accordancewith controlling conducted by the controller 60.

[0360] As mentioned above, according to the second reproducing apparatus41 and the reproducing method that is composed of the steps P1 throughP10 of the present invention, an information recording medium 1 isloaded on.

[0361] Further, the second reproducing apparatus 41 and the reproducingmethod is designed for coping with the reproducing light 99, which isgenerated by the light emitting element 50 a having a single wavelengthλ within the range of 350 nm to 450 nm and the objective lens 50 bhaving the numerical aperture NA of 0.75 to 0.9. Therefore, the secondreproducing apparatus 41 and the reproducing method can suitablyreproduce information that is recorded in the recording layer 12 of theinformation recording medium 1. At the same time, they can perform indexreproduction of a data stream by reproducing an auxiliary informationthereto.

[0362] Furthermore, in case that an auxiliary information containsinformation related to reproduction laser power other than an addressinformation, it is acceptable for a power value of the light emittingelement 50 a to be set or to be renewed by extracting the informationrelated to reproduction laser power from the read-out auxiliaryinformation.

[0363] An NA of the objective lens 50 b is large, so that sphericalaberration caused by thickness error of the light transmitting layer 11of the information recording medium 1 becomes extremely large.Consequently, spherical aberration is compensated by adjusting anoptical system in the pickup 50. Actually, in the step P2, for example,the spherical aberration can be compensated by adjusting the opticalsystem to maximize an output of differential signal after focusing. If acorrective lens not shown is installed in the pickup 50, for example, itis possible to find a maximum point of differential signal by changing adistance between the corrective lens and another optical element such asthe objective lens 50 b.

[0364] Further, compensating spherical aberration can be conducted byobserving a total sum signal. More specifically, in the step P10, thecompensation can be realized by adjusting an optical system as mentionedabove such that an output of the total sum signal is adjusted to bemaximal.

[0365] With respect to spherical aberration that is compensated byobserving a differential signal, it is also acceptable for compensationto be conducted by observing a differential signal of a microscopicpattern that is disposed in a predetermined specific area.

[0366] Further, in case that spherical aberration is compensated byobserving a total sum signal, it is also acceptable that test data isrecorded on a land portion “L” or a groove portion “G” in apredetermined specific area and the compensation is conducted byobserving a total sum signal of the test data. Particularly, in casethat the information recording medium 1 is in disciform, thesecompensating methods of spherical aberration are desirable to beperformed in an area, where a user never records or reproduces data,such as an area allocated in the inner circumference area.

[0367] With referring to FIG. 36, a recording apparatus for recordingany of the information recording mediums 1 through 5 according to thepresent invention is explained, wherein the information recording medium1 represents the information recording mediums 1 though 5 genericallyfor simplifying the explanation hereinafter.

[0368]FIG. 36 is a block diagram of a recording apparatus 90 forrecording an information recording medium 1 according to the presentinvention. The recording apparatus 90 is an apparatus for recordinginformation in the recording layer 12 of the information recordingmedium 1, and composed of at least a recording unit provided with alight emitting element, which emits recording light having a wavelengthλ of 350 nm to 450 nm and has a noise level of less than RIN −125 dB/Hz,and an objective lens having a numerical aperture NA of 0.75 to 0.9, anda control unit, which controls the recording unit so as to record theinformation recording medium 1 by irradiating the recording lightexclusively on a land portion “L” of the information recording medium 1.

[0369] Actually, the recording apparatus 90 is similar to the secondreproducing apparatus 41 shown in FIG. 34 except for followings: thedemodulator 54 is replaced by a modulator 82 for modulating an originaldata and a waveform converter 83 for transforming a modulated signalfrom the modulator 82 into a waveform suitable for recording on aninformation recording medium 1, which are connected in series, and theI/F 55 is replaced by an interface (I/F) 81 for receiving an externalsignal to be recorded. Other components are exactly the same as those ofthe second reproducing apparatus 41, so that explanations for the samefunctions and operations are omitted.

[0370] Further, the recording apparatus 90 is an apparatus for recordinga computer data, for example, at a predetermined address newly orrecording a HDTV program or a movie continuously from a predeterminedaddress by a video recorder.

[0371] The modulator 82 is such a modulator that converts an 8-bitoriginal data into 16 bits, in case of the EFM plus modulation method.The waveform converter 83 transforms a modulated signal that is receivedfrom the modulator 82 into another waveform that is suitable forrecording on an information recording medium 1. Actually, the waveformconverter 83 is such a converter that converts a modulated signal into arecording pulse, which satisfies a recording characteristic of therecording layer 12 of the information recording medium 1. In case thatthe recording layer 12 is composed of a phase change material, forexample, a so-called multi-pulse is formed. In other words, themodulated signal is divided into a unit of channel bit or less than theunit of channel bit, and recording power is changed into a rectangularwaveform, wherein peak power, bottom power, erase power and a pulse timeduration, which constitute a multi-pulse, are adjusted in accordancewith a direction of the controller 60.

[0372] With referring to FIGS. 36 and 37, an operation of the recordingapparatus 90 is explained next.

[0373]FIG. 37 is a flow chart showing a recording method of aninformation recording medium 1 by using the recording apparatus 90 shownin FIG. 36. As shown in FIG. 37, an operation of the recording apparatus90, that is, a recording method of the information recording medium 1 byusing the recording apparatus 90 is composed of at least followingsteps. The information recording medium 1 is loaded on the turntable 53of the recording apparatus 90 (step R1). The reproducing light 99 fromthe pickup 50 is converged and focused on the microscopic pattern 20formed in the information recording medium 1 (step R2), and is madetracking (step R3). A differential signal is produced from reflectedreproducing light 99 that is reflected by the recording later 12 (stepR4). A reference clock signal is extracted from the differential signal(step R5). Revolution of the motor 51 is controlled by the extractedreference clock signal (step R6). An auxiliary information is extractedfrom the differential signal (step R7). An address information isextracted from the extracted auxiliary information (step R8). A positionof the pickup 50 is controlled by the extracted address information andanother address information inputted externally (step R9). An inputtedsignal is demodulated and the recording light 89 is emitted (step R10).

[0374] More specifically, the information recording medium 1 is loadedon the turntable 53 that can control revolution of the informationrecording medium 1 to the circumferential direction (the step R1).Succeedingly, the reproducing light 99 is emitted from the lightemitting element 50 a of the pickup 50 through the objective lens 50 band converged on the microscopic pattern 20 of the information recordingmedium 1 (the step R2). More accurately, the reproducing light 99 isfocused on the microscopic pattern 20, which is disposed at a depth of0.07 mm to 0.12 mm that is equivalent to the thickness of the lighttransmitting layer 11. Then, the reproducing light 99 is conducted to atrack either the groove portion “G” or the land portion “L” (the stepR3). The tracking is conducted by selecting a portion previouslydecided. However, as mentioned above, selecting the land portion “L” ismost preferable. The differential signal “(Ia+Ib)−(Ic+Id)” in the radialdirection is produced from reflected reproducing light 99 that isreflected by the recording layer 12 and picked up by the pickup 50 (thestep R4). The produced differential signal is transmitted to thereference clock demodulator 57 and a clock signal is produced (the stepR5).

[0375] Further, the clock signal is transmitted to the controller 60 soas to control a number of revolutions of the turntable 53 and controlsrevolution of the motor 51 by way of the servo controller 52 (the stepR6).

[0376] The differential signal is transmitted to the auxiliaryinformation demodulator 56 at the same time, and an auxiliaryinformation is read out (the step R7). At this moment, an addressinformation out of various auxiliary information is extracted (the stepR8). The extracted address information is compared with another addressinformation that is utilized for indexing data, which is inputted to thecontroller 60. In case that the extracted address information does notcoincide with the other address information, the controller 60 sends asignal to the servo controller 52 and instructs the servo controller 52to search. The searching is conducted such that a number of revolutionsof the motor 51 is reset to a specific number of revolutions, whichcorresponds to a radius between the motor 51 and the pickup 50,according to movement in the radial direction of the pickup 50 whilescanning the movement of the pickup 50 in the radial direction.

[0377] Furthermore, during a process of scanning, an address informationoutputted from the address information demodulator 56, which receives adifferential signal from the pickup 50, is compared with a predeterminedaddress information. The searching is continued until they coincide witheach other (the step R9). When they coincide with each other, scanningin the radial direction is interrupted and reproduction is switched overto a recording operation. In other words, data inputted form the I/F 81is demodulated by the demodulator 82 in accordance with controllingconducted by the controller 60. The modulated data is inputted into thewaveform converter 83 in accordance with the controlling conducted bythe controller 60 and finally, the demodulated data is transformed intoa format that is suitable for recording, and outputted to the pickup 50(the step R10).

[0378] In the pickup 50, the recording light 89 is generated by changingrecording power to a predetermined recording power that is designated bythe waveform converter 83, and irradiated on the information recordingmedium 1. Consequently, the original data is recorded at a predeterminedaddress in the information recording medium 1.

[0379] In addition thereto, the recording light 89 can read out thedifferential signal “(Ia+Ib)−(Ic+Id)” in the radial direction and anaddress can be extracted from the auxiliary information demodulator 56even while recording. Accordingly, limited area recording as far as anaddress that is required by a user can be conducted.

[0380] As mentioned above, according to the recording apparatus 90 andthe recording method that is composed of the steps R1 through R10 of thepresent invention, an information recording medium 1 is loaded on.

[0381] Further, the recording apparatus 90 and the recording method isdesigned for coping with the reproducing light 99 and the recordinglight 89, which are generated by the light emitting element 50 a havinga single wavelength λ within the range of 350 nm to 450 nm and theobjective lens 50 b having the numerical aperture NA of 0.75 to 0.9.Therefore, the recording apparatus 90 and the recording method cansuitably record information in the recording layer 12 of the informationrecording medium 1. At the same time, they can reproduce even auxiliaryinformation and can conduct random indexing for recording.

[0382] Furthermore, in case that an auxiliary information containsinformation related to recording strategy for generating multi-pulsesuch as peak power, erase power, and pulse interval other than anaddress information, it is acceptable that a setting value of thewaveform converter 83 is designated or renewed by extracting thesestrategic information from the read-out auxiliary information.

[0383] More, it is possible to combine the above-mentioned recordingmethod and the reproducing method together. For example, an additionalstep of confirming whether or not recording on an information recordingmedium 1 is conducted correctly by reproducing the recorded informationrecording medium 1 can be added after the information recording medium 1is recorded by the recording method that is composed of the steps R1through R10. The additional step of confirming is conducted byreproducing the recorded area by the reproducing light 99, and bycomparing data to be recorded and another data to be reproduced.

[0384] Moreover, by extracting an address information from an auxiliaryinformation, the additional step of confirming can be compared with theaddress information hereat. In case that data not recorded properly isfound by the comparing, an address information corresponding to theoriginal data is recorded in a specific area at the inner circumferencearea and/or the outer circumference area of the information recordingmedium 1. In other words, in case that an error is found when confirmingby reproducing after recording, the address information is recorded in aspecific area of the information recording medium 1. Consequently, anaddress information having error can be recognized by referring to thespecific area when reproducing data recorded by a user.

[0385] Further, it is possible to reproduce the recorded data excludingonly data corresponding to the address information.

[0386] Accordingly, reproduction without error can be enabled.

[0387] Furthermore, in case that data not recorded properly is found bythe comparing, it is acceptable that the defective data is recorded inanother area having another address information together with recordingan address information corresponding to the original data in a specificarea at the inner circumference area and/or the outer circumference areaof the information recording medium 1. By this process, not onlyreproducing without error but also compensating a defective part can beconducted, so that it is more effective.

[0388] The light emitting element 50 a that is used in the first andsecond reproducing apparatuses 40 and 41 is detailed hereupon. The lightemitting element 50 a is defined as either a semiconductor laser ofgallium nitride system compound or a laser having a second harmonicgenerating element. However, these individual laser elements have aparticular laser noise respectively. In the case of a semiconductorlaser of gallium nitride system compound, particularly, its noise levelis relatively high. According to our measurement for the noise level, alaser RIN (Relative Intensity Noise) of a laser having a second harmonicgenerating element is −134 dB/Hz that is a similar noise level to thatof a red-light emitting semiconductor laser having a wavelength of 650nm approximately being used for a DVD system.

[0389] On the other hand, in case of a semiconductor laser of galliumnitride system compound, its laser RIN is −125 dB/Hz. That is, the laserRIN of the semiconductor laser of gallium nitride system compound islarger that that of the laser having a second harmonic generatingelement by 9 dB. The noise is added to a reproduced signal from theinformation recording medium 1 and results in deteriorating an SIN ofthe reproduced signal extremely. In other words, in case that asemiconductor laser of gallium nitride system compound is adopted forthe light emitting element 50 a of the first and second reproducingapparatuses 40 and 41, a signal characteristic is deteriorated.Therefore, a guide for designing DVD system that has been obtained by uscan not be applied for the first and second reproducing apparatuses 40and 41 by just shifting the guide proportionally.

[0390] Accordingly, in view of that a particular noise inherent in alaser is added to a reproduced signal from the information recordingmedium 1 when reproduced by these first and second reproducingapparatuses 40 and 41, it is essential for an information recordingmedium to have a signal characteristic in which a worsen componentcaused by the particular noise inherent in a laser is compensated.

[0391] With respect to the information recording medium 5 according tothe fifth embodiment of the present invention, by changing a depth ofthe microscopic pattern 20, that is, height difference between a grooveportion “G” and a land portion “L” formed on the substrate 13, severalvariations of the information recording medium 5 are manufactured. Thoseinformation recording mediums are reproduced by the second reproducingapparatus 41 that is installed with a semiconductor laser of galliumnitride system compound having a laser RIN of −125 dB/Hz as the lightemitting element 50 a, and a relation between reflectivity and an errorrate of reproduced signal is studied.

[0392] In addition thereto, recording is conducted by the recordingapparatus 90 under an ideal recording condition such that an error ratedecreases maximally.

[0393] Reflectivity could be defined as an output of reproduced signal.In case that the recording layer 123 is constituted by a phase changematerial, reflectivity is an index correlating to brightness of therecording layer 123 in a crystalline state. More specifically, aninformation recording medium 5 is recorded with a modulation signal ofthe above-mentioned (d, k) code. The information recording medium 5 isloaded in the second reproducing apparatus 41 so as to be flat orwithout declining, and then a recorded signal is reproduced. Thereproduced signal of a DC system outputted from the pickup 50 isconnected to an oscilloscope, and reflectivity is obtained from a signalhaving the maximum mark length (k+1). In the case of the 17PPmodulation, for example, in which “d” and “k” is “one” and “seven”respectively, a minimum mark length (d+1) is 2T and a maximum marklength (k+1) is 8T. Therefore, reflectivity is calculated from anabsolute reflectivity calibration line by measuring I8H.

[0394] Further, an error rate is obtained by measuring a reproducedsignal obtained through the demodulator 54.

[0395] Result of measuring modulation amplitude and error rate by thesecond reproducing apparatus 41 after recording the 17PP modulation bythe recording apparatus 90 is shown in FIG. 38.

[0396]FIG. 38 is a graph exhibiting a relation between reflectivity anderror rate. As shown in FIG. 38, there is existed an apparent mutualrelation between reflectivity and error rate. It is apparent that anerror rate drastically increases in accordance with reflectivity thatdecreases. In case that a practical error rate is defined as 3×10⁻⁴ thatis the figure specified by the several standards such as the DVDStandard, necessary reflectivity is more than 2%.

[0397] Further, the information recording medium 5 may warp bytemperature change in the surrounding of use. Consequently, withassuming that the information recording medium 5 inclines by the orderof 0.7 degree as the same angle as a DVD disc, an error rate increasesmore than coma aberration caused compositively by conditions such that awavelength λ is within a range of 350 nm to 450 nm, a numerical apertureNA is within a range of 0.75 to 0.9, and a thickness of the lighttransmitting layer 11 is within a range of 0.07 mm to 0.12 mm.

[0398] Furthermore, in case that the information recording medium 5 isinclined by 0.7 degree, it is found by an experimental measurement thatthe error rate of 3×10⁻⁴ is equivalent to 0.7×10⁻⁴ when the incline iszero degree. In other words, the error rate of 0.7×10⁻⁴ is essential foractual use.

[0399] Accordingly, it is found that practical reflectivity is more than5%.

[0400] As mentioned above, in the case that the semiconductor laser ofgallium nitride system compound is used as a light emitting element, anoise is added to a reproduced signal. Therefore, by constitutingreflectivity of the information recording medium 5 to be more than 5%,an error rate can be practically reduced to the same degree as the DVDSpecification.

[0401] Further, it is found by an experimental study that thecorrelation between reflectivity and error rate shown in FIG. 38 can beobtained by any of the modulation methods mentioned above. It is causedby that a signal output almost saturates in any modulation methods whenthe maximum mark length (k+1) exceeds 6T approximately and becomes aconstant value although the maximum mark length (k+1) varies by themodulation methods.

[0402] Accordingly, one reflectivity obtained by recording theinformation recording medium 1 by the 17PP modulation method, wherein“d” is one and “k” is seven, is a same value as the other reflectivityobtained by the EFM plus modulation method, wherein “d” is two and “k”is ten. In the above-mentioned case, if the information recording medium1 is replaced by the information recording medium 5, the same result isobtained.

[0403] In consideration of the reproducing characteristic of the firstand second reproducing apparatuses 40 and 41 and the recording apparatus90, the information recording mediums 1 through 5 according to thepresent invention of which reflectivity is designated to be more than 5%are explained above.

[0404] In consideration of a general characteristic of the first andsecond reproducing apparatuses 40 and 41 and the recording apparatus 90of which light emitting element is constituted by a semiconductor laserof gallium nitride system compound, and a physical characteristic of therecording layer 12 or 123, which is constituted by a phase changematerial, totally, a range of more practical reflectivity of theinformation recording mediums 1 through 5 that is necessary forrealizing a total system is explained next.

[0405] A maximal output of semiconductor laser of gallium nitride systemcompound is merely 30 mW. In a recording apparatus, it is general thatan output of a pickup decreases almost one fifth of a laser output dueto a coupling efficiency of optical elements applied for a wavelength λwithin a range of 350 nm to 450 nm. In other words, a laser powerdecreases down to 6 mW on the surface of the information recordingmediums 1 through 5 although a laser of which output is 30 mW is used.

[0406] On the contrary, in order to realize phase change recording inexcellent contrast, a recording power is desirable to be designated ashigh as possible. Therefore, the information recording mediums 1 through5 are essential to be recorded by the recording power of the order of 6mW. Consequently, an absorbency index and transmittance of the recordinglayer 12 or 123 of the information recording mediums 1 through 5 isessential to be a higher value relatively.

[0407] A particular noise inherent in a semiconductor laser of galliumnitride system compound and increasing noise in a reproducing apparatusutilizing the semiconductor laser of gallium nitride system compound ismentioned above. However, it is also necessary to pay attention to thata noise depends upon a reproduction laser power when designing a totalsystem. The inventors of the present invention measure a laser noisewhile changing a reproduction laser power. In case of a semiconductorlaser of gallium nitride system compound, it is found that a noiseincreases in accordance with a laser power that decreases, and foundparticularly that there is existed a critical point at 0.35 mW of laserpower on a surface of information recording medium. In other words, whenthe laser power is lower than 0.35 mW, a noise increases extremely.Consequently, a reproduction laser power on the surface of theinformation recording mediums 1 through 5 is essential to be more than0.35 mW.

[0408] With respect to a physical characteristic of the recording layer12 or 123, there is existed a phenomenon such that the recording layer12 or 123 is damaged thermally and a recorded record mark “M” vanisheswhen a reproduction laser power is increased. Accordingly, it isnecessary for a reproduction laser power to be set to lower than aparticular value. Particularly, in case of reproducing light having awavelength λ within a range of 350 nm to 450 nm, an energy density of aspot “S” formed on a surface of recording layer is larger than that of ared-light emitting semiconductor laser of which wavelength is within arange of 635 nm to 830 nm, for example. Therefore, a reproduction laserpower is set relatively low. However, a permissible range ofreproduction laser power is narrowed due to the above-mentioned minimumlimit for reproduction laser power. In order to increase tolerance forreproduction laser power, that is, in order to set a reproduction laserpower larger, an absorbency index and transmittance of the recordinglayer 12 or 123 of the information recording mediums 1 through 5 isessential to be a lower value relatively.

[0409] As mentioned above, in consideration of the generalcharacteristic of the first and second reproducing apparatuses 40 and 41and the recording apparatus 90 of which light emitting element isconstituted by a semiconductor laser of gallium nitride system compound,and the physical characteristic of the recording layer 12 or 123, whichis constituted by a phase change material, totally, it is concluded thatan information recording medium in which a record mark “M” on therecording layer 12 or 123 is hardly vanished by a reproduction laserpower of more than 0.35 mW is required while a recording power is in theneighborhood of 6 mW. In other words, an absorbency index andtransmittance is essential to be within a predetermined range. A sum ofan absorbency index and transmittance and reflectivity is one, so thatreflectivity is essential to be within a predetermined range as well.

[0410] The inventors of the present invention experimentally study areflectivity range that satisfies the above-mentioned limitations, andfind an optimal reflectivity range of 12% to 26%. Hereinafter, an actualmanufacturing process of the information recording medium 5 is detailedas embodiments 1 through 7 and comparative examples 1 and 2.

[0411] [Embodiments 1 through 7]

[0412]FIG. 39 is a chart exhibiting reflectivity and reproductioncharacteristics of embodiments 1 through 7 and comparative examples 1and 2.

[0413] Samples of embodiments 1 through 7 and comparative examples 1 and2 are manufactured as a phase-change recording type informationrecording medium 5. A polycarbonate plate having a thickness of 1.1 mmis utilized for a substrate 13. A reflective layer 121, a firstprotective layer 122, a recording layer 123, and a second protectivelayer 124 is constituted by Ag₉₈Pd₁Cu₁, ZnS—SiO₂ (80:20 at mol %),Ge₈Sb₆₉Te₂₃, and ZnS—SiO₂ (80:20 at mol %) respectively, wherein eachfilm thickness of the reflective layer 121, the first protective layer122, the recording layer 123, and the second protective layer 124follows figures shown in FIG. 39 respectively. Finally, a polycarbonateplate having a thickness of 0.10 mm is laminated on the secondprotective layer 124. Consequently, the samples of the embodiments 1through 7 and the comparative examples 1 and 2 are completed as aninformation recording medium 5.

[0414] An auxiliary information area 200 and a reference clock area 300is formed continuously on a land portion “L” of each informationrecording medium 5 without being interrupted. The auxiliary informationarea 200 is composed of a frequency-shift keying modulation wave 262 ofwhich fundamental wave is a sinusoidal wave (or a cosine wave), whereina phase difference between a higher frequency section and a lowerfrequency section is “2π+(π/2.5)”.

[0415] Further, a phase is selected so as to be that the waveformcontinues at a point where a frequency changes over from higher to loweror vice versa.

[0416] Furthermore, the auxiliary information area 200 is recordedgeometrically on a sidewall as a wobbling groove.

[0417] In addition thereto, a single-frequency wave 350 of whichfundamental wave is a sinusoidal wave (or a cosine wave) is recordedgeometrically on a sidewall as a wobbling groove.

[0418] The information recording medium 5 is designed for recording orreproducing by using a pickup installed with optical elements of whichwavelength λ is 405 nm and an NA is 0.85, and a pitch “P” between landportions “L” is 0.32 μm.

[0419] Further, the reflective layer 121 and the recording layer 123 isformed by the DC sputtering process, and the first and second protectivelayers 122 and 124 are formed by the AC sputtering process in anatmosphere of argon gas of 5 mTorr.

[0420] Furthermore, a vacuum chamber used for sputtering is sufficientlyexhausted as low as less than 1×10⁻⁶ Torr.

[0421] More, each completed information recording medium 5 isinitialized by irradiating a laser beam on the recording layer 123through the light transmitting layer 11, and the recording layer 123 isphase changed from an amorphous state in lower reflectivity to acrystalline state in higher reflectivity.

[0422] Each information recording medium 5 is loaded on the recordingapparatus 90 equipped with a pickup installed with optical elements ofwhich wavelength λ is 405 nm and an NA is 0.85. A recording signal isrecorded on a land portion “L” with a modulation signal of which minimummark length (equal to 2T) is designated to be 0.149 μm by the 17PPmodulation method, wherein “d” and “k” is “one” and “seven”respectively.

[0423] Further, a differential signal reproduced from the referenceclock area 300 of each information recording medium 5 is transmitted tothe reference clock demodulator 57 and revolution of the turntable 53 iscontrolled by the obtained reference clock. By controlling the turntable53 as mentioned above, a record mark “M” having a desired length isconducted to be recorded accurately. With respect to a recordingcondition, a recording peak power is 6.0 mW, a bias power is 2.6 mW, abottom power between multi-pulses and a cooling pulse is 0.1 mW, and alinear velocity is 5.3 m/s respectively.

[0424] Furthermore, the recording is conducted by a signal, which istransformed into a so-called multi-pulse by the waveform converter 83,and by adopting a 3-level power modulation method, wherein each pulsewidth of a head pulse and a succeeding pulse is designated to be 0.4times the recording period 1T and a pulse width of cooling pulse isdesignated to be 0.4 times the recording period 1T.

[0425] Succeedingly, the information recording medium 5 is loaded on thesecond reproducing apparatus 41 shown in FIG. 34 equipped with thepickup 50 having a wavelength λ of 405 nm and a numerical aperture NA of0.85. and a land portion “L” is reproduced.

[0426] With respect to evaluation items, there is existed reflectivityand modulation amplitude that is equal to “(I8H−I8L)/I8H”, which areobtained from a total sum signal, reproduction laser power at limit ofdeterioration, reproduction error rate of record mark “M” obtained fromthe demodulator 54, and reproduction error rate of address informationrecorded in the auxiliary information area 200 that is obtained from theauxiliary information demodulator 56. The reproduction laser power atlimit of deterioration is obtained as follows: at first reproducing theinformation recording medium 5 by the reproduction laser power of 0.3mW, then measuring a laser power that deteriorates reproduction bygradually increasing reproduction laser power from 0.3 mW.

[0427] With respect to the reproduction laser power at limit ofdeterioration and the reproduction error rate of record mark “M” and theerror rate of address information out of these evaluation items, theyare judged by comparing with a reference value and decided whether ornot they are acceptable.

[0428] A reference value of reproduction laser power at limit ofdeterioration is designated to be 0.35 mW. Each sample of theembodiments 1 through 7 and comparative examples 1 and 2 is judgedwhether it is reproduced by the laser power of more than 0.35 mW orless. Consequently, as shown in FIG. 39, a sample of which reproductionlaser power at limit of deterioration is more than 0.35 mW is judged asacceptable and marked “Good”. On the contrary, another sample of whichreproduction laser power at limit of deterioration is less than 0.35 mWis judged as defective and marked “Not”.

[0429] Further, with respect to a reference value of reproduction errorrate of reproduced signal, samples of which reproduction error rate isless than 0.7×10⁻⁴ are judged as acceptable and marked “Good”, and othersamples of which reproduction error rate is more than 0.7×10⁻⁴ arejudged as defective and marked “Not”.

[0430] Furthermore, with respect to a reference value of address errorrate, samples of which address error rate is less than 5% are judged asacceptable and marked “Good”, wherein 5% is a limit of restoring anaddress information by error correction. On the contrary, other samplesof which address error rate is more than 5% is judged as defective.

[0431] In addition thereto, each figure of reflectivity and modulationamplitude and reproduction laser power at limit of deterioration, andeach judgement of reproduction laser power at limit of deterioration,error rate of reproduced signal, and address error rate with respect tothe embodiments 1 through 7 and the comparative examples 1 and 2 isexhibited in FIG. 39.

[0432] As shown in FIG. 39, the embodiments 1 through 7, which aremanufactured by designating reflectivity to be within a range of 12% to26%, are excellent in every evaluation items, so that they can satisfyperformance as a total system.

[COMPARATIVE EXAMPLE 1]

[0433] A sample of the comparative example 1 is manufactured bydesignating reflectivity to be 11.0% and evaluated the same items as thesamples of the embodiments 1 through 7. Result of the evaluation isshown in FIG. 39. According to the evaluation, reproduction isdeteriorated at 0.34 mW. Therefore, it is concluded that the recordinglayer 123 is too sensitive. Consequently, an information recordingmedium of which reflectivity is less than 11% is not suitable for atotal system.

[COMPARATIVE EXAMPLE 2]

[0434] A sample of the comparative example 2 is manufactured bydesignating reflectivity to be 28.2% and evaluated the same items as thesamples of the embodiments 1 through 7. Result of the evaluation isshown in FIG. 39. In the case of the comparative example 2, reproductionis not deteriorated. However, a reproduction error rate is excessively,so that the comparative example 2 is defective. The defect is caused bythat modulation amplitude is too small as small as 0.389. In otherwords, sensitivity of the recording layer 123 is too low, so that it issupposed that recording in sufficient contrast is not conducted.Consequently, an information recording medium of which reflectivity ismore than 28% is not suitable for a total system.

[0435] According to the evaluation result of the embodiments 1 through 7and the comparative examples 1 and 2, reflectivity that is suitable forestablishing a total system is supposed to be within a range of 12% to26%. The 17PP modulation, where “d” is one and “k” is seven, is appliedfor the embodiments 1 through 7 and the comparative examples 1 and 2 asa recording signal. However, applying the “D4.6” modulation, where “d”is one and “k” is nine, also obtains the same result.

[0436] Further, applying the “D8-15” modulation, where “d” is two and“k” is ten, brings the same result as well.

[0437] Furthermore, in the embodiments 1 through 7, the auxiliaryinformation area 200 is constituted by the frequency-shift keyingmodulation wave 262. However, the phase-shift keying modulation wave 272also brings the same result. The amplitude-shift keying modulation wave252 brings the same result as well.

[0438] More, in the embodiments 1 through 7, the auxiliary informationarea 200 and the reference clock area 300 is continuously formed withoutinterruption. However, in case that the auxiliary information area 200is connected to the reference clock area 300 with sandwiching a lineargroove having a length of 1 mm, the recording apparatus 90 can notconduct recording. Because, a reference clock can not be extracted fromthe linear groove, so that revolution servo can not be applied to theturntable 53.

[0439] Moreover, in the embodiments 1 through 7, the auxiliaryinformation area 200 and the reference clock area 300 is formed on aland portion “L”. In case that the auxiliary information area 200 andthe reference clock area 300 is formed on a groove portion “G”, therecording apparatus 90 can not conduct recording. Because, the recordinglight 89 of the recording apparatus 90 is focused on the land portion“L”, so that a reproduced signal from the reference clock area 300 isinterfered by a reference clock signal twice. Consequently, an extremelyunstable clock can only be extracted.

[0440] By designating reflectivity to be more than 5%, particularly, tobe within a range of 12% to 26% as mentioned above, the informationrecording mediums 1 through 5 according to the present invention cancompensate the problem of adding a particular noise inherent in asemiconductor laser of gallium nitride system compound utilized for thefirst and second reproducing apparatuses 40 and 41 to a reproducedsignal.

[0441] A method of regulating modulation amplitude to be within apredetermined range as a second method of compensating the problem ofadding a particular noise inherent in a semiconductor laser of galliumnitride system compound to a reproduced signal is explained next.

[0442] By changing each material and each layer thickness of thereflective layer 121, the first protective layer 122, the recordinglayer 123 and the second protective layer 124 of the informationrecording medium 5 according to the fifth embodiment of the presentinvention, several samples of information recording mediums aremanufactured. These samples are reproduced by the first reproducingapparatus 40 in which a semiconductor laser of gallium nitride systemcompound having a laser RIN of −125 dB/Hz is adopted as the lightemitting element 50 a, and evaluated with respect to a relation betweenmodulation amplitude and an error rate of reproduced signal. Recordinghereupon is conducted by the recording apparatus 90 under most idealrecording conditions so as to decrease an error rate to the utmostlimit.

[0443] Reproduction modulation amplitude is an output of reproducedsignal. In case that the recording layer 123 is constituted by a phasechange material, modulation amplitude is an index correlating toreflectivity contrast between crystal and amorphous. More specifically,the modulation amplitude is obtained by recording a modulation signal ofthe (d, k) code in the information recording medium 5 by the recordingapparatus 90.

[0444] The information recording medium 5 is loaded on the secondreproducing apparatus 41 in flat, that is, without being inclined and arecorded signal is reproduced, and then a reproduced signal in DC systemoutputted from the pickup 50 is connected to a oscilloscope.Consequently, modulation amplitude is obtained. from a signal (k+1)having the maximum mark length that is utilized for the (d, k) codingmethod. In the case of the “8-16” modulation method that is utilized forthe DVD system, for example, the maximum mark length is 14T. Therefore,by measuring I14L and I14H as specified in the JIS Standard X6241/1997,modulation amplitude, that is, (I14H−I14L)/I14H is calculated.

[0445] On the other hand, in the case of the 17PP modulation method, themaximum mark length is 8T. Therefore, by measuring I8L and I8H,modulation amplitude, that is, (I8H−I8L)/I8H is calculated.

[0446] Further, in the case of the “D4, 6” modulation method, themaximum mark length (k+1) is 10T. Therefore, by measuring I10L and I10H,modulation amplitude, that is, (I10H−I10L)/I10H is calculated.

[0447] Furthermore, an error rate is obtained, by measuring a reproducedsignal obtained through the demodulator 54.

[0448] Result of measuring modulation amplitude and an error rate by thefirst reproducing apparatus 40 after recording a signal modulated by the17PP modulation method by the recording apparatus 90 is shown in FIG.40.

[0449]FIG. 40 is a graph exhibiting a relation between modulationamplitude and error rate. As shown in FIG. 40, there is existed anapparent relationship between modulation amplitude and error rate. It isapparent that an error rate drastically increases in accordance withmodulation amplitude that decreases. In case that a practical error rateis defined as 3×10⁻⁴ that is the FIG. specified by the several standardssuch as the DVD Standard, necessary modulation amplitude is more than0.34.

[0450] Further, an information recording medium 5 may warp bytemperature change in the surrounding of use. Consequently, withassuming that the information recording medium 5 inclines by the orderof 0.7 degree that is the same angle as a DVD disc, an error rateincreases more than coma aberration caused compositively by conditionssuch that a wavelength λ is within a range of 350 nm to 450 nm, anumerical aperture NA is within a range of 0.75 to 0.9, and a thicknessof the light transmitting layer 11 is within a range of 0.07 mm to 0.12mm.

[0451] When the information recording medium 5 is inclined by 0.7degree, it is found by an actual measurement that the error rate of3×10⁻⁴ is equivalent to 0.7×10⁻⁴ when the incline is zero degree. Inother words, the error rate of 0.7×10⁻⁴ is essential in consideration ofincline while actual use.

[0452] Accordingly, it is found that practical modulation amplitude ismore than 0.4.

[0453] As mentioned above, in consideration of the phenomenon of addingnoise when a semiconductor laser of gallium nitride system compound isused for a light emitting element, an error rate can be suppressed tothe same level as the DVD Standard and becomes a practical level if aninformation recording medium 5 is constituted such that modulationamplitude is more than 0.4.

[0454] In addition thereto, with respect to the correlation betweenmodulation amplitude and error rate as shown in FIG. 40, it isexperimentally understood that almost similar results are obtained fromany modulation methods applied for the above-mentioned (d, k) code. Asignal output is almost saturated by any of these modulation methodswhen the maximum mark length exceeds 6T although a maximum mark length(k+1) may vary by the modulation method. Consequently, a value ofmodulation amplitude obtained from an information recording medium 1recorded by the 17PP modulation method, for example, is the same as thatobtained from the information recording medium 1 recorded by the “D4, 6”modulation method. The same results are obtained although theinformation recording medium 1 is replaced with an information recordingmedium 5.

[0455] Further details are explained as embodiments 8 through 12 next.In addition, samples of comparative examples 3 through 5 are alsomanufactured for the purpose of comparison.

[0456] [Embodiment 8]

[0457] A sample of an embodiment 8 is manufactured as a phase-changerecording type information recording medium 5. A polycarbonate platehaving a thickness of 1.1 mm is utilized for a substrate 13. Areflective layer 121, a first protective layer 122, a recording layer123, and a second protective layer 124 is constituted by Ag₉₈Pd₁Cu₁,ZnS—SiO₂ (80:20 at mol %), Ag—In—Sb—Te, and ZnS—SiO₂ (80:20 at mol %)respectively. Finally, a polycarbonate plate having a thickness of 0.10mm is laminated on the second protective layer 124 as a lighttransmitting layer 11. The sample of the embodiments 8 (hereinaftersimply referred to as embodiment 8) is manufactured as an informationrecording medium 5.

[0458] An auxiliary information area 200 and a reference clock area 300is formed continuously on a land portion “L” of the informationrecording medium 5 of the embodiment 8 without being interrupted. Theauxiliary information area 200 is composed of a frequency-shift keyingmodulation wave 262 of which fundamental wave is a sinusoidal wave (or acosine wave), wherein a phase difference between a higher frequencysection and a lower frequency section is “2π±(π/2.5)”.

[0459] Further, a phase is selected so as to be that the waveformcontinues at a point where a frequency changes over from higher to loweror vice versa.

[0460] Furthermore, the auxiliary information area 200 is recordedgeometrically on a sidewall as a wobbling groove.

[0461] In addition thereto, a single-frequency wave 350 of whichfundamental wave is a sinusoidal wave (or a cosine wave) is recordedgeometrically on a sidewall as a wobbling groove.

[0462] The embodiment 8 is designed for recording or reproducing byusing a pickup installed with optical elements of which wavelength λ is405 nm and an NA is 0.85. A pitch “P” between land portions “L” of theembodiment 8 is 0.32 μm.

[0463] Further, the reflective layer 121 and the recording layer 123 isformed by the DC sputtering process, and the first and second protectivelayers 122 and 124 are formed by the AC sputtering process in anatmosphere of argon gas of 5 mTorr.

[0464] Furthermore, a vacuum chamber used for sputtering process issufficiently exhausted as low as less than 1×10⁻⁶ Torr.

[0465] More, the embodiment 8 is initialized by irradiating a laser beamon the recording layer 123 through the light transmitting layer 11, andthe recording layer 123 is phase-changed from an amorphous state inlower reflectivity to a crystalline state in higher reflectivity.

[0466] The embodiment 8 is loaded on the recording apparatus 90 equippedwith a pickup installed with optical elements of which wavelength λ is405 nm and an NA is 0.85. A recording signal is recorded on a landportion “L” with a modulation signal of which minimum mark length thatis equal to 2T is designated to be 0.149 μm by the 17PP modulationmethod.

[0467] Further, a differential signal reproduced from the referenceclock area 300 of the embodiment 8 is transmitted to the reference clockdemodulator 57, and then revolution of the turntable 53 is controlled bythe obtained reference clock. By controlling the turntable 53 asmentioned above, a record mark “M” having a desired length is conductedto be recorded accurately.

[0468] With respect to a recording condition, a recording peak power is6.0 mW, a bias power is 2.6 mW, a bottom power between multi-pulses anda bottom power of a cooling pulse is 0.1 mW respectively, and a linearvelocity is 5.3 m/s.

[0469] Furthermore, the recording is conducted by a signal, which istransformed into a so-called multi-pulse by the waveform converter 83. A3-level power modulation method is adopted, wherein each pulse width ofa head pulse and a succeeding pulse is designated to be 0.4 times therecording period 1T and a pulse width of cooling pulse is designated tobe 0.4 times the recording period 1T.

[0470] Succeedingly, the embodiment 8 is loaded on the secondreproducing apparatus 41 equipped with the pickup 50 having a wavelengthλ of 405 nm and a numerical aperture NA of 0.85, and then a land portion“L” is reproduced.

[0471] With respect to evaluation items, there is existed modulationamplitude that is equal to “(I8H−I8L)/I8H” and obtained from a total sumsignal, reproduction laser power at limit of deterioration, reproductionerror rate of record mark “M” obtained from the demodulator 54, andreproduction error rate of address information recorded in the auxiliaryinformation area 200 that is obtained from the auxiliary informationdemodulator 56.

[0472] A signal of which modulation amplitude that is equal to“(I8H−I8L)/I8H” is 0.52 is reproduced from a total sum signal.Succeedingly, an excellent error rate as low as 2×10⁻⁵ is obtained froma reproduced signal outputted from the demodulator 56. Consequently,data that do not come into question in practical application areextracted.

[0473] Further, an error rate of address information obtained from theauxiliary information demodulator 56 is the order of 1% in a recordedsection, so that address data is restored excellently.

[0474] Furthermore, in case that an error rate of address information isless than 5% when reproducing after recorded in the recording layer 123,almost errorless data can be restored by a error correction process.Consequently, less than 5% is suitable for the error rate of addressinformation.

[0475] [Embodiment 9]

[0476] A sample of embodiment 9 (hereinafter simply referred to asembodiment 9) is identical to the embodiment 8 except for the modulationmethod. In case of the embodiment 9, a recording signal is modulated bythe “D4, 6” modulation method and the minimum mark length that is equalto 2T is 0.154 μm. The embodiment 9 is recorded and reproduced as thesame manner as the embodiment 8. A signal of which modulation amplitudethat is equal to “(I10H−I10L)/I10H” is 0.60 is reproduced whenreproducing a land portion “L”. Succeedingly, an excellent error rate aslow as 8×10⁻⁶ is obtained from a reproduced signal. Consequently, datathat do not come into question in practical application are extracted.

[0477] Further, an error rate of address information is the order of 1%in a recorded section, so that address data are restored excellently.

[0478] [Embodiment 10]

[0479] A sample of embodiment 10 (hereinafter simply referred to asembodiment 10) is identical to the embodiment 8 except for themodulation method. In case of the embodiment 10, a recording signal ismodulated by the “D8-15” modulation method and the minimum mark lengththat is equal to 3T is 0.185 μm. The embodiment 10 is recorded andreproduced as the same manner as the embodiment 8. A signal of whichmodulation amplitude that is equal to “(I12H−I12L)/I12H” is 0.63 isreproduced when reproducing a land portion “L”. Succeedingly, anexcellent error rate as low as 4×10⁻⁶ is obtained from a reproducedsignal. Consequently, data that do not come into question in practicalapplication are extracted.

[0480] Further, an error rate of address information is the order of 1%in a recorded section, so that address data are restored excellently.

[0481] [Embodiment 11]

[0482] A sample of embodiment 11 (hereinafter simply referred to asembodiment 11) is identical to the embodiment 8 except for themodulation method and recording of auxiliary information. In case of theembodiment 11, auxiliary information data are recorded in a wobblingshape by the phase-shift keying modulation wave 272.

[0483] Further, a recording signal is modulated by the 17PP modulationmethod and the minimum mark length that is equal to 2T is 0.149 μm.

[0484] The embodiment 11 is recorded and reproduced as the same manneras the embodiment 8. A signal of which modulation amplitude that isequal to “(I8H−I8L)/I8H” is 0.60 is reproduced when reproducing a landportion “L”. Succeedingly, an excellent error rate as low as 2×10⁻⁵ isobtained from a reproduced signal. Consequently, data that do not comeinto question in practical application are extracted.

[0485] Furthermore, an error rate of address information is the order of0.1% in a recorded section, so that address data are restoredexcellently.

[0486] [Embodiment 12]

[0487] A sample of embodiment 12 (hereinafter simply referred to asembodiment 12) is identical to the embodiment 8 except for themodulation method. In case of the embodiment 12, auxiliary informationdata are processed through the base-band modulation by the Manchestercoding method.

[0488] Further, the auxiliary information data processed through thebase-band modulation are modulated to be the frequency shift keyingmodulation wave 262 shown in FIG. 22, wherein a phase relation between ahigher frequency section and a lower frequency section is 2π±(π/2.5).

[0489] Furthermore, the embodiment 12 is recorded with a wobbling shapeby the frequency-shift keying modulation method, wherein a phase isselected such that a waveform continues at a point where a frequencychanges over.

[0490] More, a recording signal is modulated by the “D4, 6” modulationmethod and the minimum mark length that is equal to 2T is 0.154 μm.

[0491] The embodiment 12 is recorded and reproduced as the same manneras the embodiment 8. A signal of which modulation amplitude that isequal to (I10H−I10L)/I10H is 0.60 can be reproduced when reproducing aland portion “L”. Succeedingly, an excellent error rate as low as 8×10⁻⁶is obtained from a reproduced signal. Consequently, data that do notcome into question in practical application can be extracted.

[0492] Moreover, an error rate of address information is the order of 1%in a recorded section, so that address data are restored excellently.

[COMPARATIVE EXAMPLE 3]

[0493] A sample of comparative example 3 (hereinafter simply referred toas comparative example 3) is identical to the embodiment 8 except forrecording that is conducted to a groove portion “G” of the informationrecording medium 5 according to the embodiment 1. A signal havingmodulation amplitude of 0.38 is reproduced by reproducing a grooveportion “G”. Succeedingly, an error rate of 4×10⁻³ is obtained from areproduced signal. Consequently, data, which contain many defective anderratic portions that are impossible to correct, are extracted.

[0494] Further, address data are completely disordered, and extractingdata is impossible.

{COMPARATIVE EXAMPLE 4}

[0495] A sample of comparative example 4 (hereinafter simply referred toas comparative example 4) is identical to the embodiment 8 except forthe thickness of the light transmitting layer 11. In case of thecomparative example 4, a thickness of the light transmitting layer 11 is0.06 mm. A signal having modulation amplitude of 0.46 is reproduced.However, an eye pattern is obscure. Succeedingly, an error rate of6×10⁻³ is obtained from a reproduced signal. Consequently, data, whichcontain many defective and erratic portions that are impossible tocorrect, are extracted.

[0496] Further, an error rate of address information is 10% in arecorded section, so that address data are defective and contain manyerratic portions that are impossible to correct.

[0497] Furthermore, the comparative example 4 is easily scratched by ascratch test such that the objective lens 50 b is forced to contact withthe comparative example 4 and to slide. Consequently, the comparativeexample 4 is not suitable for an information recording medium.

[COMPARATIVE EXAMPLE 5]

[0498] A sample of comparative example 5 (hereinafter simply referred toas comparative example 5) is identical to the embodiment 8 except forthe thickness of the light transmitting layer 11. In case of thecomparative example 5, a thickness of the light transmitting layer 11 is0.13 mm. A signal having modulation amplitude of 0.38 is reproduced.However, an eye pattern is obscure. Succeedingly, an error rate of9×10⁻³ is obtained from a reproduced signal. Consequently, data, whichcontain many defective and erratic portions that are impossible tocorrect, are extracted.

[0499] Further, an error rate of address information is 10% in arecorded section, so that address data are defective and contain manyerratic portions that are impossible to correct.

[0500] Accordingly, in consideration of the result of evaluation beingconducted to the embodiments 1 through 7 and the comparative examples 1and 2, which are summarized in FIG. 40, and the embodiments 8 through 12and the comparative examples 3 through 5, it is concluded that a rangeof modulation amplitude that is suitable for establishing a total systemis more than 0.4.

[0501] Details of the information recording mediums 1 through 5, thefirst and second reproducing apparatuses 40 and 41, and the recordingapparatus 90 according to the present invention are explainedhereinbefore.

[0502] While the invention has been described above with reference tospecific embodiment thereof, it is apparent that many changes,modification and variations in the arrangement of equipment and devicescan be made without departing from the invention concept disclosedherein. For example, in the case of the information recording medium 1,the microscopic pattern 20 is constituted by only one layer. However,the information recording medium 1 can be expanded to an informationrecording medium in which one set of layers constituted by the recordinglayer 12 and the light transmitting layer 13 is repeatedly laminated aplurality of times and a plurality of layers of microscopic patternssuch as two layers, three layers and four layers is formed.

[0503] Further, with respect to the first and second reproducingapparatuses 40 and 41 and the recording apparatus 90, the presentinvention provides not only the apparatuses themselves but also theiroperations.

[0504] Furthermore, the present invention provides the reproducingmethod and the recording method that is conducted by replacing eachoperation of apparatuses with each step of procedures of the operationsrespectively.

[0505] More, the present invention provides computer programs thatexecute each step of the reproducing method and the recording method.

[0506] Moreover, the preset invention provides a recording andreproducing apparatus that combines the first or second reproducingapparatus and the recording apparatus, and provides a recording andreproducing method that combines the reproducing method and therecording method.

[0507] In addition thereto, the present invention provides a system thatis constituted by combining the information recording medium, thereproducing apparatus, the recording apparatus, the reproducing method,and the recording method totally.

[0508] According to the present invention, as mentioned above, there isprovided an information recording medium that is composed of at least asubstrate having a microscopic pattern, which is constituted by acontinuous substance of approximately parallel grooves formed with agroove portion and a land portion alternately, a recording layer formedon the microscopic pattern, and a light transmitting layer having athickness of 0.07 mm to 0.12 mm, which is formed on the recording layer.

[0509] Further, with defining that a pitch between the groove portionsor the land portions is “P” and a wavelength of reproducing light is λand a numerical aperture of an objective lens is NA, the microscopicpattern is formed with satisfying a relation of P≦λ/NA.

[0510] Furthermore, recording is conducted in accordance with either oneof reflectivity difference and phase difference caused by recording ineither the land portion or the groove portion so as to be more than 5%for reflectivity while the wavelength λ is within the range of 360 nm to450 nm and the numerical aperture NA is within the range of 0.75 to 0.9.

[0511] Accordingly, making recording density of the informationrecording medium higher can be realized as well as reducing cross erase.

[0512] In addition thereto, an error rate can be suppressed down to apractical level. In other words, by combining with a reproducingapparatus, a recording apparatus, a reproducing method, and a recordingmethod, a total system can be established.

[0513] Particularly, designating reflectivity to be within a range of12% to 26% can establish a total system in combination with areproducing apparatus and a recording apparatus.

[0514] Further, according to the present invention, recording isconducted in accordance with either one of reflectivity difference andphase difference caused by recording in either the land portion or thegroove portion so as to be more than 0.4 for modulation amplitude.Consequently, making recording density of the information recordingmedium higher can be realized as well as reducing cross erase.

[0515] Furthermore, an error rate can be suppressed down to a practicallevel. In other words, by combining with a reproducing apparatus, arecording apparatus, a reproducing method, and a recording method, atotal system can be established.

[0516] An auxiliary information such as address data is recordedgeometrically in a part of microscopic pattern by the amplitude-shiftkeying modulation method. Therefore, recorded data can be demodulatedeven under low C/N condition.

[0517] Further, an auxiliary information such as address data isrecorded geometrically in a part of microscopic pattern by thefrequency-shift keying modulation method. Therefore, recorded data canbe demodulated by a simplified circuitry. Particularly, by utilizing afrequency-shift keying modulation in which a phase is selected such thata wave continues at a point of changing a frequency, a reproductionenvelope is made constant and stable reproduction is enabled.

[0518] Furthermore, an auxiliary information such as address data isrecorded geometrically in a part of microscopic pattern by thephase-shift keying modulation method. Therefore, recorded data can bereproduced even under low C/N condition by demodulating the modulateddata by the synchronous detection method.

[0519] Particularly, phase difference between a higher frequency sectionand a lower frequency section, which constitute a frequency-shift keyingmodulation wave, is set to ±π/2.5, excellent signal demodulation isenabled by the synchronous detection method.

[0520] Furthermore, a reference clock is recorded in succession to anauxiliary information in a part of microscopic pattern, so thatcontrolling revolution of a reproducing apparatus and a recordingapparatus is enabled. Recording by stabilized length of record mark canbe conducted, particularly when recording.

[0521] It should be understood that many modifications and adaptationsof the invention will become apparent to those skilled in the art and itis intended to encompass such obvious modifications and changes in thescope of the claims appended hereto.

What is claimed is:
 1. An information recording medium at leastcomprising: a substrate having a microscopic pattern constituted by acontinuous substrate of grooves formed with a groove portion and a landportion alternately; a recording layer formed on the microscopic patternfor recording information; and a light transmitting layer formed on therecording layer, the information recording medium is furthercharacterized in that the microscopic pattern is formed with satisfyinga relation of P≦λ/NA, wherein P is a pitch of the land portion or thegroove portion, λ is a wavelength of reproducing light for reproducingthe recording layer, and NA is a numerical aperture of an objectivelens, and that the land portion is formed with wobbling so as to beparallel with each other for both sidewalls of the land portion, andthat an auxiliary information based on data used supplementally whenrecording the information and a reference clock based on a clock usedfor controlling a recording speed when recording the information isrecorded alternately and continuously.
 2. The information recordingmedium in accordance with claim 1, wherein the information is recordedin the recording layer corresponding to only the land portion by atleast either one change of reflectivity difference and refractive indexdifference in the recording layer so as to be more than 5% forreflectivity.
 3. The information recording medium in accordance withclaim 1, wherein the information is recorded in the recording layercorresponding to only the land portion by at least either one change ofreflectivity difference and refractive index difference in the recordinglayer so as to be more than 0.4 for modulation amplitude of signalrecording.
 4. The information recording medium in accordance with claim1, wherein the auxiliary information is recorded by at least any onemodulation wave of amplitude-shift keying modulation wave,frequency-shift keying modulation wave, and phase-shift keyingmodulation wave.
 5. A reproducing apparatus for reproducing a recordinglayer of an information recording medium comprising: a substrate havinga microscopic pattern constituted by a continuous substrate of groovesformed with a groove portion and a land portion alternately; therecording layer formed on the microscopic pattern for recordinginformation; and a light transmitting layer formed on the recordinglayer, the information recording medium is further characterized in thatthe microscopic pattern is formed with satisfying a relation of P≦λ/NA,wherein P is a pitch of the land portion or the groove portion, λ is awavelength of reproducing light for reproducing the recording layer, andNA is a numerical aperture of an objective lens, and that the landportion is formed with wobbling so as to be parallel with each other forboth sidewalls of the land portion, and that an auxiliary informationbased on data used supplementally when recording the information and areference clock based on a clock used for controlling a recording speedwhen recording the information is recorded alternately and continuously,the reproducing apparatus comprising: a light emitting element foremitting reproducing light having a wavelength λ of 350 nm to 450 nm anda noise of less than RIN (Relative Intensity Noise) −125 dB/Hz; areproducing means equipped with an objective lens having a numericalaperture NA of 0.75 to 0.9; and a control means for controlling thereproducing means to irradiate the reproducing light only on the landportion for reproducing.